Keithley 263 Service manual

WARRANTY

Keithley Instruments. Inc. warrants this product to be free from defects in material and workmanship for a period of l 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 OFTHE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.

Keithley Instruments, Inc. * 28775 Aurora Road * Cleveland, OH 44139 - 440-248-0400 *Fax: 440-248-6168 * http://www.keithley.com

Model 263 Calibrator/Source

Instruction Manual

01987, Keithley Instruments, Inc.

Cleveland, Ohio, U.S.A.

Fifth Printing, November 2000

Document Number: 263-901-01 Rev. E

Manual Print History

The print history shown below lists the printing dates of all Revisions and Addenda created for this manual. The Revision Level letter increases alphabetically as the manual undergoes subsequent updates. Addenda, which are released between Revisions, contain important change information that the uw should incorporate immediately into the manual. Addenda are numbered sequentially. When a new Revision is created, all Addenda associated with the previous Revision of the manual are incorporated into the new Revision of the manual. Each new Revision includes a revised copy of this print history page.

Revision A (Document Number 263-901-01) ................................................. October 1987

Addendum A (Document Number 263-901-02). ............................................. October 1988

Revision B (Document Number 263-901-01) ............................................. December 1988

Revision C (Document Number 263-901-01) ................................................... March 1991

Revision D (Document Number 263-901-01). ................................................. August 1992

Addendum D (Document Number 263-901-02) ......................................... September 1993

Revision E (Document Number 263-901-01). ............................................. November 2000

Safe& Precautions

The following safety precautions should be observed before using this product and any associated instrumentation. Although some instruments and accessories would normally be used with non-hazardous voltages, there are situations where hazardous conditions may be present.

This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury. Read the operating information carefully before using the product.

Tbe 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 arc adequately trained.

Operators USC the product for its intended function. They must he trained in electrical safety procedures and proper use of the instrw mea. They must be protected from electric shock and contact with hazardous live circuits.

Maintenance personnel perform routine procedures on the product

to keep it operating, for example, setting the lint 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 sewicc

pelS0”llC.l.

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.

Users of this product must be protected from electric shock at all times. The responsible body must onsure that users are prevented access and/or insulated from every connection point. In some cases, connections must he exposed to potential human contact. Product users in these circumstances must he 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.

As described in the International Electrotechnical Commission (IEC) Standard IEC 664, digital multimeter measuring circuits (e.g., Kcithley Models 175A. 199,2000,2001, 2002, and 2010) are

Installation Category II. All other instruments’ signal terminals are Installation Category I and must not he connected to mains.

Do not connect switching cards directly to unlimited power circuits.

They are intended to be used with impedance limited sources.

NEVER connect switching cards directly to AC mains. When connecting sources to switching cards, install protective devices to limit fault current and voltage to the card.

Before operating an instrument, make sure the line cord is connected to a properly grounded power receptacle. Inspect the connecting cables, test leads, and jumpers for possible wear, cracks, or breaks before each use.

For maximum safety, do not touch the product, test cables, or any

other instruments while power is applied to the circuit under test. ALWAYS remove power from the entire test system and discharge any capacitors before: connecting or disconnecting cables or jumpers, installing or removing switching cards, or making internal changes, such as installing or removing jumpers.

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.

Do not touch any object that could provide a current path to the common side of the circuit under test or power line (earth) gruund. Always make measurements with dry hands while standing on a dry, insulated surface capable of withstanding the voltage being measured.

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

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.

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 aproduct, replace with same type and rating

for continued protection against tire 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 a&plied to the device under test. Safe operation requires the use of a lid interlock.

Ifa@. wire recommended in the user documentation.

Then symbol on an instrument indicates that the user should refer to the operating instructions located in the manual.

Then sure 1000 volts or more, including the combined effect of normal and common mode voltages. Use standard safety precautions to

twoid personal contact with these voltages.

FCEW is present, connect it to safety earth ground using the

symbol on an instrument shows that it can source ormca-

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 lostrumerits. 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 tbc original component. (Note that se-

lected parts should be purchased only through Keitbley 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 ox chassis (e.g., data acquisition board for installation into a

computer) should never require cleaning if handled according to in-

structions. If the board becomes contaminated and operation is af-

fected, the board should be returned to the factory for proper

cleaning/servicing.

Rev. lo/99

263 Calibrator/Source

Table of Contents

SECTION 1 - General Information

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.7.1

1.7.2

1.8

1.9

SECTION 2 - Getting Started

INTRODUCTION. .................

FEATURES. .......................

WARRANTY INFORMATION .......

MANUAL ADDENDA .............

SAFETY TERMS AND SYMBOLS.

SPECIFICATIONS .................

UNPACKING AND INSPECTION ...

Shipment Contents ...............

Additional Documentation. .......

REPACKING FOR SHIPMENT ......

OPTIONAL ACCESSORIES .........

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

I-1 l-1 l-1 1-l 1-l 1-l l-2 l-2 l-2 1-2 l-2

2.1

2.2

2.3

2.4

2.4.1

2.4.2

2.4.3

INTRODUCTION. FRONT PANEL FAMILIARIZATION. REAR PANEL FAMILIARIZATION CALIBRATOR/SOURCE OPERATION.

rower up

Test Connections.

Basic Sourcing Procedure

SECTION 3 - Operation

3.1

3.2

3.2.1

3.2.2

3.2.3

3.2.4

3.2.5

3.2.6

3.3

3.3.1

3.3.2

3.3.3

3.4

3.4.1

3.4.2

3.5

3.5.1

3.5.2

3.6

3.6.1

3.6.2

3.7

3.7.1

3.7.2

3.7.3

INTRODUCTION ..........................................................................

I’OWERUI’I’ROCEDURE ..................................................................

LineVoltage .............................................................................

LinePowerConnections ..................................................................

PowerSwitch ............................................................................

PowerUpSelfTest .......................................................................

Power Up Configuration. .................................................................

WarmUpPeriod

OUTPUTCHARACTERISTICS ..............................................................

VoltageSource ...........................................................................

ResistanceSource ........................................................................

CurrentandChargeSource ................................................................

FUNCTION AND RANGE SELECTION.

FunctionSelection .......................................................................

RangeSelection ..........................................................................

DATAENTRY .............................................................................

AdjustMethod ..........................................................................

KeypadMethod .........................................................................

OPERATEANDZERO .....................................................................

Operate .................................................................................

Zero ....................................................................................

GUARD ..................................................................................

GuardedOhms

GuardedAmpsandCoulombs .............................................................

GuardedVolts

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

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

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

......

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

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

.........

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

2-l 2-l 2-3 2-4 2-5 2-5 2-5

3-l 3-l

3.1 3-2 3-2 3-2 3-2 3-2 3-2 3-2 3-4 34 3-6 3-6 3-6 3-7 3-7 3-8 3-9 3-9 3-9 3-10 3-11 3-15 3-19

3.8

3.9

3.9.1

3.9.2

3.9.3

3.10

3.10.1

3.10.2

3.10.3

3.10.4

3.11

3.11.1

3.11.2

3.11.3

PREAMP OUT

FRONTI'ANELI'ROGRAMS

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

ProgramdISP

Programtc ..............................................................................

SOURCINGTECHNIQUES .................................................................

Connections. ............................................................................

SourcingOhms .......................................................................... 3-22

SourcingVolts ........................................................................... 3-23

SourcingAmpsandCoulombs

SOURCING CONSIDERATIONS

Temperaturecompensation

BurdenVoltage .......................................................................... 3-26

Guarding ...............................................................................

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

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

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

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

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

3-19 3-20

3-21 3-21 3-21

3-24 3-26 3-26

3-27

SECTION 4

4.1

4.2

4.2.1

4.2.2

4.3

4.4

4.4.1

4.4.2

4.5

4.5.1

4.5.2

4.5.3

4.6

4.6.1

4.6.2

4.6.3

4.6.4

4.6.5

4.6.6

4.6.7

4.7

4.7.1

4.7.2

4.7.3

4.7.4

4.7.5

4.7.6

4.7.7

4.7.8

4.7.9

4.7.10

4.7.11

4.7.12

4.7.13

4.7.14

4.7.15

4.7.16

4.7.17

4.8

INTRODUCTION .........................................................................

BUSCONNECTIONS ......................................................................

vpical Contro!led Systems

Cable Connecttons ... PRlMARYADDRESSPROGRAMMING CONTROLLERPROGRAMMING

Controller Handler Software ..............................................................

Interface BASIC Programming Statements FRONT PANEL ASPECTS OF IEEE-488 OPERATION

BusErrors ..............................................................................

NumberErrors ..........................................................................

CalibrationStorageMessages

GENERALBUSCOMMANDS

REN(RemoteEnable) IFC(InterfaceClear). LLO(LocalLockout) GTL(GoToLocal)andLocal

DCL(DeviceClear) ......................................................................

SDC(SelectiveDeviceClear)

SPE, SPD (Serial Polling).

DEVICE-DEPENDENT COMMANDS. .......................................................

Programmingoverview

A(Calibration) ..........................................................................

C(TemperatureCompensation) F(Function)

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

J (Self-test), .............................................................................

K (EOI). L (Calibration; Low Temperature Point).

M (SRQ Mask and Serial I’oII Byte Format) ..................................................

O(Operate) .............................................................................

R(Range) ...............................................................................

u (Status).

V(OutputValue) ........................................................................

W (Guard), .............................................................................

X(Execute) .............................................................................

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

Z(Zero) ................................................................................

TIMING CONSIDERATIONS

- IEEE-486

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

Programming

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

, ...............................................................................................

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

41 4-l 41 4-2 4-3

4-4 44 44 4-5 4-5 4-5 4-6 4-6 4-6 4-7 4-7 4-7 4-7

4-8 4-8 49 49 412 4-13 414 415 416

4-17 4-18 4-19 4-21 4-22 4-23 4-26 4-27 4-28 4-29 430 431

SECTION 5 - Applications

5.1

5.1.1

5.1.2

5.2

5.2.1

5.2.2

5.2.3

5.2.4

5.2.5

5.3

5.3.1

5.3.2

5.3.3

5.3.4

5.3.5

5.3.6

5.3.7

5.4

5.4.1

5.4.2

5.4.3

5.4.4

5.4.5

5.4.6

5.4.7

5.5

5.5.1

5.5.2

5.5.3

5.5.4

5.5.5

INTRODUCTION

Calibration Applications Sourcing Applications

MODEL485CALIBRATION..

Calibration Storage Enable Required Equipment Environmental Conditions Front Panel Calibration IEEE-488 Bus Calibration.

MODEL617CALIBRATION..

CalibrationJumper RequiredEquipment Environmental Conditions Calibrationsequence Manual Calibration Adjustments. Front Panel Digital Calibration. IEEE-488 Bus Digital Calibration.

CALIBRATING OTHER PICOAMMETERSIELECTROMETERS

Model 480 Picoammeter Calibration.

Model 619 Electrometer Calibration

Model 614 Electrometer Calibration

Model 642 Electrometer Calibration Model 610C Electrometer Calibration. Model 602 Electrometer Calibration Model 616 Electrometer Calibration

SOURCING APPLICATIONS

Current Suppression Galvanometric Measurements Low Resistance “LindecK’ Measurements Resistivity Measurements Diode Characterization

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

5-1 5-l 5-l 5-l 5-1 5-l 5-2 5-2 5-3 5-4 5-4 5-5 5-5 5-5 5-6 5-7 5-11 5-14 5-14 5-14 5-15

5-16 5-16 5-18 5-19 5-19 5-19 5-20 5-21 5-21 5-21

SECTION 6 - Performance Verification

6.1

6.2

6.3

6.4

6.5

6.6

6.6.1

6.6.2

6.6.3

6.6.4

6.6.5

6.6.6

INTRODUCTION

ENVIRONMENTALCONDITIONS lNITIALCONDITIONS

RECOMMENDEDTESTEQUIPMENT

PERFORMANCEVERIFICATION RECORD VERIFICATIONPROCEDURES

VOLTSAccuracyVerification 1~AccuracyCheck AMPSZeroOffsetChecks AMPS (200vA-2mA) Accuracy Checks AMPS (20pA-2uA) Accuracy Check AMPS V/R Functional Checks

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

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

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

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

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

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

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

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

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

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

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

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

6-l 6-l 6-l 6-1 6-2

6-2 6-2 6-3 6-4 6-6 6-7 6-7

iii

SECTION 7 - Principles of Operation

7.1 INTRODUCTION .........................................................................

7.2 OVERALL FUNCTIONAL DESCRIPTION.

7.3 VOLTAGESOURCE

7.4

7.5 CURRENT SOURCES

7.5.1 Passive (AMPS V/R) Current Source

7.5.2 Active(AMPS)CurrentSource

7.6

7.7

7.8 DIGITALCIRCUITRY

7.8.1 Microcomputer ..........................................................................

7.8.2 MemoryElements

7.8.3

7.8.4 IEEE-488Bus ............................................................................

7.9

7.10 MAINPOWERSUPPLY

OHMSSOURCE ...........................................................................

CHARGE SOURCES TEMPERATURECOMPENSATION

DeviceSelection

DISPLAYCIRCUITRY

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

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

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

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

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

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

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

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

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

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

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

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

SECTION 8 - Maintenance

8.1

8.2

8.3

8.4

8.4.1

8.4.2

8.4.3

8.4.4

8.4.5

8.4.6

8.4.7

8.4.8

8.5

8.6

8.7

8.7.1

8.7.2

8.7.3

8.7.4

8.7.5

8.7.6

8.7.7

8.7.8

8.8

INTRODUCTION ............................................

LINE VOLTAGE SELECTION FUSE REPLACEMENT.

CALIBRATION ..............................................

Calibration Overview Recommended Calibration Equipment Environmental Conditions. Cool-down Period

Calibration Switch ..........................................

Calibration Record. Front Panel Calibration.

IEEE-488 Bus Calibration Program SPECIAL HANDLING OF STATIC SENSITIVE DEVICES. DISASSEMBLY INSTRUCTIONS

TROUBLESHOOTING ........................................

Recommended Test Equipment.

Power Up Self Test.

Display Test and Software Revision

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

Logic and Switching FET States.

VoltageSourceChecks

Electrometer Amplifier Check

Digital and Display Circuitry Checks. HANDLING AND CLEANING PRECAUTIONS

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

7-l 7-l 7-1 7-7 7-7 7-8 7-8 7-10 7-10 7-10 7-10 7-11 7-11 7-11 7-11 7-12

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

............................ 8-1

............................ 8-2

............................ 8-3

............................ 8-10

............................ 8-13

............................ 8-15

............................ 8-16

............................ 8-17

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

............................ 8-20

............................ 8-22

8-l 8-l

8-20

SECTION 9 - Replaceable Parts

9.1 INTRODUCTION .........................................................................

9.2 ELECTRICAL PARTS LISTS.

9.3 MECHANICAL PARTS.

9.4

9.5

9.6

ORDERINGINFORMATION

FACTORYSERVICE.. .....................................................................

COMPLETE LOCATION DRAWINGS AND SCHEMATIC DIAGRAMS

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

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

............................................................... 9-l

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

9-l 9-l 9-l

9-l Y-l

APPENDIX A

APPENDIX B

Interface Function Codes.

APPENDIX C

ASCII Character Codes and IEEE-488 Multiline Interface Command Messages.

APPENDIX D

IBM PC/AT and CEC PC < > 4R8 Interface Programming.

APPENDIX E

Controller Frograms........................................................................ E-l

APPENDIX F

IEEE-488 Bus Overview.

APPENDIX G

Performance Verification and Calibration Records.

B-l

C-l

D-l

F-l

G-l

List of Tables

SECTION 3 - Operation

3-l 3-2 3-3 3-4 3-5

Power Up Default Conditions Sourcing Guarded Ohms to Keithley Electrometers. Additional Ohms Specifications. Temperature Compensated Functions/Ranges, Output Resistance of Passive Sources,

SECTION 4 - IEEE-488 Programming

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

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

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

................................................ 3-26

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

3-2 3-14 3-23

3-27

4-l 4-2 4-3 4-4 General Bus Commands and Associated BASIC Statements. 4-s Device-Dependent Command Summary.

IEEE-488 Contact Designation BASIC Statements Necessary to Send Bus Commands

IEEE-486FrontPanelMessages ..............................................................

............................................................... 4-2

.......................................... 4-5

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

SECTION 5 - Applications

5-l 5-2 5-3 5-4

Model 485 Range Calibration. Model 617 Amps Calibration Model 617 Volts Calibration

Model617OhmsCalibration ...............................................................

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

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

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

SECTION 6 - Performance Verification

6-l 6-2 6-3 6-4 6-5 6-h 6-7

Recommended Test Equipment.

VOLTSAccuracyChecks ....................................

IkfiAccuracyChecks

AMPS Zero Offset Checks. ..................................

AMPS (200pA-2mA) Accuracy Checks. AMPS (20pA-2pA) Accuracy Checks

AMPS V/R Functional Checks. ..............................

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

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

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

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

SECTION 7 - Principles of Operation

7-l 7-2 7-3

VoltageSourceRanges ......................................................................

OHMSSourceRanges ......................................................................

Current Range Resistances

.................................................................. 7-R

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

4-5 4-6 4-10

5-2 5-8 5-9 5-9

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

7-3 7-7

vii

SECTION 8 - Maintenance

8-l 8-2

8-3 84 8-5

8-6

8-7

8-8

8-9

a-10

8-11

8-12

8-13

8-14

8-15

8-16

8-17

8-18 8-19

LineFuseSelection . . .._........................._......._.................................

Recommended Calibration Equipment

“Cold “Coki” Low Ohms Calibration . “Cold

“Hot VoltsCahbrahon.....................................................................

“Hot LowOhmsCallbratlon...............................................................

“Hot” High Ohms Calibration.

“Cold” High Ohms Calibration (Direct Measurement Method)*. “Hot” High Ohms Calibration (Direct Measurement Method)*.

Recommended Troubleshooting Equipment.

rowersupplychecks...................................................................... 8-16

Volts Logic and Switching States.

Amps and Coulombs Logic and Switching States Ohms Logic and Switching States*

VoltageSourceChecks*..................................................................... 8-20

Electrometer Amplifier Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

DisplayCircuitryChecks...................................................................

Volts Calibration.

High Ohms Calibration.

I, n

8-2 8-3

8-7 8-7

8-7

8-8 8-8 8-8 8-9 8-9 8-15

8-17 8-18 8-19

8-20

8-21 8-21

List of Illustrations

SECTION 2 - Getting Started

2-l 2-2 2-3 24 Data Entry Controls-Keypad Method.

SECTION 3 - Operation

3-l 3-2

3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 3-11 3-12 Sourcing Guarded 3-13 3-14 3-15 3-16 3-17 3-18

3-19 3-20 3-21 3-22 3-23

3.24 Burden Voltage Considerations 3-25 3-26

Model263FrontFanel......................................................................

Model263I~earPanel.....................................................,,...............

Data Entry Controls -Adjust Method.

LineVoltageSwitch

voltagesource .............................................................................

ExternalSource

Active Current Source (Unguarded).

Passive(V/R)CurrentSource ................................................................

Data Entry Controls -Adjust Method,

Data Entry Controls - Keypad Method.

UnguardedCircuit .........................................................................

GuardedCircuit ...........................................................................

OhmsOutputConhgurabons Sourcing Guarded Ohms to Electrometer that has a Selectable Guarded Input.

Amps/Coulombs Output Configurations Sourcing Amps to a Feedback Picoammeter Sourcing Guarded Amps to a Shunt Picoammeter Using an Input Adapter

GuardingforHighImpedanceLoad ..........................................................

UsingI’REAMI’OUTGuard

VoltsOutputConfiguration .................................................................

Using I’reamp Out to Monitor Load Voltage. output Connector Configuration Unguarded Sourcing to Electrometer Connecting External Voltage Source to Model 263.

SourcingtoaLoad .........................................................................

UnguardedTriaxCable .....................................................................

GuardedTriaxCable .......................................................................

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

............................................................................ 3-4

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

Ohms to

Electrometer Using an Input Adapter,

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

.............................................................. 3-21

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

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

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

....................................................... 3-9

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

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

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

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

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

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

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

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

2-2 2-4

2-6 2-7

3-1 3-3

3-5 3-6 3-7

3-l 0 3-11 3-12

3-12 3-13 3-16 3-17

3.17 3-18 3-l 8 3-19

3-22

3.24 3-25 3-27 3-28 3-29

SECTION 4 - IEEE-488 Programming

4-l 4-2

4-3 4-4 45 4-6 4-7 4-8 4-9 410

SystemSpes ......................................................................

IEEE-488Connector ................................................................

IEEE-488Connections ..............................................................

Model 263 Rear Panel IEEE-488 Connector ContactAssignments

GeneralDataFormat ...............................................................

SRQ Mask and Serial Poll Byte Format. UO Machine Status Word (Default Conditions Shown) UlErrorStatusWord

IJ2DataStatusWord ...............................................................

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

,..... ‘I-2

............................................ 4-3

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

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

4-l

4-3

4-3 4-15 4-20 4-24 4-24 4-25

SECTION 5 - Applications

5-l Model 485 Calibration Connections 5-2 Calibration Jumper Location (Model 617) 5-3 Input Offset Adjustment Locations (Model 617). 5-4 5-5 5-6 Connections for External Voltage Source. 5-7 5-8 5-9 Model642Ca~bratlon 5-10 Model610CCalibration.. 5-11 5-12 Model602AccuracyChecks 5-13 5-14 5-15

5-16

5-17 5-18

Connections for Model 617 Voltage Source Calibration. Connections for Model 617 Calibration

Model480Calbration Sourcing Guarded Ohms to Electrometer Using an Input Adapter.

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

Model 610C Ohms Accuracy Checks (XGQ)

Model602OhmsAccuracyChecks(SlGn)

Nulling Circuit

LowResistanceMeasurementConnections Resistivity Measurement Using the Model 263. Diodecharacterization DiodeCurves

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

5-3

5-5

5-6 5-7 5-10 5-10 5-14 5-15 5-16 5-17 5-18 5-19 5-19 5-20 5-21

5-22 5-22 5-22

SECTION 6 - Performance Verification

6-l VOLTSAccuracyChecks ~~.~~~~..~~.~~~~~.~~...~~~.~~~.~.~...~.~~~.~~....~.~~.~.~~~~...~~~~ 6-2

6-2 AMPSZeroOffsetChecks ,,_.,,.,,.._.,,,._...._,,,.,,.__,,..,_...,,,.__..._,...._,,..._._, 6-5

63 64

AMPS (ZOOPA and 2mA Ranges) Accuracy Checks AMPS (ZOpA-2bA Ranges) Accuracy Checks

6-6

6-7

SECTION 7 -Principles of Operation

7-1 Model 263 Simplified Diagram

7-2 VoltageSourceBlockDiagram

7-3 Pulse Width Modulation. 7-4 7-5 7-6 7-7 7-8 Active (AMPS) Current Source Circuitry. 7-9

3-PoleFilter ...............................................................................

Voltage Source Ranging Amplifier

Simplified Voltage Source Ranging Amplifier.

Passive (AMPS V/R Current Source)

Active (AMPS) Current Source

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

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

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

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

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

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

SECTION 8 - Maintenance

8-1 8-2 Calibration Switch

8-3 Volts and Low Ohms Calibration 8-4 8-5 E-6 Model263ExplodedView

Line Voltage Switch (105-125V Range Selected)

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

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

High Ohms Calibration and Voltage Offset Adjust OffsetVoltageAdjust

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

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

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

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

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

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

7-2 7-3 7-4

7-5 7-6 7-7 7-8 7-9 7-10

8-1 8-3 8-5 8-6 8-9 E-14

SECTION

General Information

1.1 INTRODUCTION

This section contains information on the Model 263 Calibrator/Source features, warranty, manual addenda, specifications, and safety terms and symbols. Also included are procedures for unpacking and inspecting the instrument, as well as a brief description of available accessories.

The information in Section 1 is arranged as follows:

1.2

Features

Warranty Information

1.3

Manual Addenda

1.4

Safety Symbols and Terms

1.5

Specifications

1.6

Unpacking and Inspection

1.7

Repacking for Shipment

1.8

Optional Accessories

1.9

1.2 FEATURES

Resistance sourcing from lkQ to 1OOGQ in decade steps.

DC voltage sourcing from OV to k19.9995V.

DC current sourcing from OA to +19.9995mA.

DC charge sourcing from OC to k19.9995lC.

. Temperature compensation for the lGR, 1OGn and lOOGO

resistors. This feature allows the unit to track the actual resistance of these resistors as the ambient temperature changes.

Two methods of data entry. The keypad method uses front panel buttons configured as a standard keypad to enter outout readines on the disolav. The adiust method uses two’adjust bu;ons to in&&t or d&rement the

displayed reading.

Zero at the touch of a button. The ZERO button toggles

the display between zero and the programmed output reading.

Fully programmable over the IEEE-488 bus.

Simple calibration: A single Keithley Model 196 DMM (or equivalent) is the only instrument needed.

1.3 WARRANTY INFORMATION

Warranty information for your Model 263 may be found inside the front cover of this manual. Should it become necessary for you to use the warranty, contact your Keithley representative or the factory for information on obtaining warranty service. Keithley Instruments, Inc maintains service facilities in the United States, West Germany, France, the Netherlands, Switzerland and Austria. Information concerning the operation, application, or service of your instrument may be directed to the applications engineer at one of these locations.

1.4 MANUAL ADDENDA

Information concerning changes or improvements to the instrument which occur after this manual has been printed will be found on an addendum sheet included with the instrument. Please be sure to read this information before attempting to operate or service the instrument.

1.5 SAFETY TERMS AND SYMBOLS

The following safety terms are used in this manual or found on the instrument.

The symbol

on the instrument indicates that the user should refer to the operating instructions in this manual for further details.

The

WARNING

heading used in this manual explains dangers that could result in personal injury or death. Always read the associated information very carefully before performing the indicated procedure.

The

CAUTION

heading used in this manual explains hazards that could damage the instrument. Such damage may invalidate the warranty.

1.6 SPECIFICATIONS

Detailed Model 263 specifications are located at the front of this manual.

l-l

GENERAL INFORMATION

1.7 UNPACKING .AND INSPECTION

The Model 263 was carefully inspected and packed before

shipment. Upon receiving the instrument, carefully un-

pack all items from the shipping carton and inspect for

any obvious signs of damage that might have occurred

during shipment. Report any damage to the shipping agent immediately. Retain the original packing material in case reshipment becomes necessary.

1.7.1 Shipment Contents

The following items are included with every Model 263 shipment:

Model 263 Calibrator/Source Model 7024-3 Triax to Traix Cable (3 ft.) Instruction Manual Quick Reference Guide

1.7.2 Additional Documentation

If an additional instruction manual is required, order the manual package, Keithley Part Number 263-901-00. The manual package includes an instruction manual and all pertinent addenda.

If an additional Quick Reference Guide is required, order Keithley Part Number 263-903-00.

1.8 REPACKING FOR SHIPMENT

Before shipment, the unit should be carefully packed in its original packing carton using all original packing

materials.

if the instrument is to be returned to Keithley Instruments for repair, complete the following:

1.9 OPTIONAL ACCESSORIES

The following accessories for the Model 263 are available from Keithley Instruments, Inc. Contact your Keithley representative or the factory for information on obtaining these accessories.

Models 1019A-1 and 1019A-2 are fixed shelf-type rack mounting kits for half-rack, 127mm (Wz in.) high instruments (such as the Model 263). The 1019A-1 kit mounts one instrument and the 1019A-2 mounts two.

Models 101951 and 1019S-2 are sliding shelf-type mounting kits for half-rack, 127mm (5% in.) high instruments (such as the Model 263). The 10195-l kit mounts one instrument and the 10195-2 mounts two.

Model 4804 is a 2-slot male BNC to 2-lug female triaxial adapter. Used to adapt the supplied triaxial output cable of the Model 263 to 2-lug BNC input connectors.

Models 6011 and 6011-10 Trixial Cables are made up of three feet of triaxial cable that is terminated with a triax plug on one end and three alligator clips on the ofher end. The Model 6011-10 is a similar cable 10 feet in length.

Model 6012 Triax to UHF Adapter allows the Model 263 to be used with accessories having UHF type connectors.

Model 6105 Resistivity Chamber is a guarded test fixture for measuring voltage and surface resistivities. The unit assures good electrostatic shielding and high insulation resistance. The complete system requires the use of an external voltage supply such as the Model 263 as well as a picoammeter. Volume resistivity up to lOWan and surface resistivity up to 10x8n can be measured in accordance with ASTM test procedures. Sheet samples 64 to 102mm (12~12 x 4”) in diameter and up to 6.4mm (IL”) thickness can be accommodated. Excitation voltages up to 1OOOV may be used.

1. On the shipping label, indicate the warranty status of

the instrument and write;

ATTENTION REPAIR DEPARTMENT

2. Complete and include the service form at the back of

this manual.

l-2

Model 6146 Triax Tee Adapter allows the simultaneous connection of two triaxial cables to the single triaxial output of the Model 263.

Model 6147 Triax to BNC Adapter allows the Model 263 output to be connected to accessories having BNC connectors.

GENERAL INFORMATION

Model 6167 Guarded Input Adapter is used to reduce effective cable capacity by driving the inner shield of the triaxial cable at guard potential. Use to

make

guarded connections from the Model 263 to Keithley Models 602, 614 and 6161 Electrometers. Triax female to triax male.

Models 6171 and 6172 3-Lug to 2-Lug Adapters-The Model 6171 is a 3-lug male to 2-lug female triadal adapter, while the Model 6172 is a 2-lug male to 3-lug female triaxial adapter.

Model 6191 Guarded Input Adapter is similar to the Model 6167 except it is used to make guarded connections from the Model 263 to the Model 619 Electrometer. Triax female to triax male.

Models 7007-l and 7007-2 are shielded IEEE-488 interface

cables with shielded connectors on each end. The 7007-l is lm (3.3 ft.) in length and the 7007-2 is 2m (6 ft.) in length.

Model 7010 Shielded IEEE to IEEE Adapter provides additional clearance between the IEEE-488 cable and rear panel, allowing easier access to switches, cables, and other connectors.

Model 7023 Female Triaxial Connector is a chassis mount connector that mates with the Models 6011 and 7024 triaxial cables.

Models 7024-3 and 7024-10 are triaxial cables terminated with 2-lug male triaxial connectors on each end. The 7024 is 0.9m (3 ft.) in length and the 7024-10 is 3.0m (10 ft.) in length.

l-311-4

SECTION 2

Getting Started

2.1 lNTRODlJCTlON

This section contains introductory information on operating pur instrument and is intended to help you get

our Model 263 u

t mcludes a brief x ‘. escnpbon of operating contmls and test connections. Once you are familiar with the material presented here, refer to Section 3 for more detailed information.

Section 2 is organized as follows:

2.2 Front Panel Familiarization: Briefly describes each

front panel control, outlines display operation, and lists where to find more detailed information in Section 3.

2.3 Rear F’mel Familiarization: Outlines each aspect of

the Model 263 rear panel including connectors and

switches.

and running as quickly as possible.

2.4 Basic Sourcing Techniques: Provides a general stepby-step procedure for sourcing resistance, voltage, current and charge.

2.2 FRONT PANEL FAMILIARIZATION

An overview of the Model 263 is given in the following paragraphs. The front panel of the instrument is shown in Figure 2-1, along with a brief description of each item.

All front panel controls except POWER are momentary contact switches. Some control buttons have an annunicator light to indicate the selected function. Some buttons have a secondary function that may be entered by pressing first SHIFT and then the desired button. All such

second

button. e controls are color-code J mto functional groups

for ease of operation.

functions are marked in ellow as is the SHIFT

2-l

GETTING STARTED

ADJUST A

ADJUSTW

CONTROL

7 //I

Figure 2-1. Model 263 Front Panel

POWER AC power switch turns unit on or off.

SHIE?

Enables access to secondary features (highlighted

in yellow).

FUNCTION BLOCK OHMS Configures the Model 263 to source 1kQ to

100GQ.

VOLTS Configures the Model 263 to source zero to

*19.9995v.

SHIFT VOLTS

Configures the Model 263 to output an external source applied to the rear panel EXT INPUT of up to +2OOV peak.

AMPS Configures the Model 263 as an active current source that can output zero to k19.9995mA.

SHIFT AMPS

Configures the Model 263 as a passive cm-

rent source (AMPS V/R) that can output zero to

+19.9995mA.

COUL Configures the Model 263 as an active coulomb source that can output zero to *199.995&.

SHIFT COUL Configures the Model 263 as a passive coulomb source (COUL V/R) that can output zero to

*199.995/K.

CONTROL BLOCK RANGE These two buttons are used to select the range

of the selected function. RANGE A upranges the instrument, while RANGE v downranges.

CURSOR These two buttons along with the adjust buttons provide one method (Adjust Method) to enter numeric data on the display. With the cursor off (see SHIFT ON/OFF), each press of a cursor button identifies

the currently selected display digit by momentarily flashing a digit segment. With the cursor on, a segment of the selected digit flashes continuously. CURSOR 4 moves the cursor from right to left and CURSOR ) moves the cursor from left to right.

SHIFT ON/OFF Toggles cursor on and off.

2-2

OETTING STARTED

ADJUST ADJUST A increments the display at the currently selected digit, while ADJUST v dec-ments the display. For example, on the 1V range with the cursor at the tenths digit, each nwmentq press of an ADJUST button will inaement or decrement the display reading by O.lV. The ADJUST buttons are also used to change front

panel program parameters. The ADJUST buttons are inoperative in the ohms function.

KEYPAD/ENTER This button along with the number buttons provide another method (Keypad Method) to enter numeric data on the display. The displa can be changed on all functions except ohms. l&h en the keypad is enabled the cursor will be at the most signifcant digit. After a number is keyed in at the mOst significant digit position, the remaining digits will zero and the cursor will move to the next less significant digit. After keying in the desired dis lay reading, press ENTER to enter the new reading an cr. &able the keypad. The ohms

display reading cannot be altered by the keypad.

SHIFT CANCEL Operational only when KEYPAD is

enabled. Pressing SHIFT CANCEL after keying in a reading usin

disable the a previous reading before KEYPAD was enabled.

the keyboard will cancel that reading and

eyboard. The display will return to the

reading

tween guarded and unguarded. A simplified schematic of the guard circuitry is located on on the rear panel.

MENU Scrolls through the available front panel programs. With a program displayed, the parameters can be changed with the ADJUST buttons. Scrollin program returns the display to the

OPERATE Toggles the instrument between the standby and operate conditions. In operate, the programmed source is available at the output.

IEEE STATUS INDICATORS TALK, LISTEN, REMOTE These three indicators app-

ly to instrument operation over the IEEE-488 bus. The REMOTE indicator shows when the instrument is in the IEEE-488 remote state. The TALK and LISTEN indicators

show when the instrument is in the talk and listen states respectively. See Section 4 for detailed infomation on operation over the bus.

norm jmode.

past the last

2.3 REAR PANEL FAMILIARIZATION

* Toggles the display between positive (+) polarity and

negative (-) polarity.

ZERO This button toggles the display between zero and

the reading that was previously displayed.

SHIFT GUARD Toggles the output configuration be-

An overview of the rear panel of the Model 263 is provided

in the following paragraphs. The rear panel is shown in

Figure 2-2. In addition to the various connectors and swit-

ches, a simplified schematic of the guard circuitry is pro-

vided. Also included is a cross reference to other sections

of the manual where more detailed information can be found.

2-3

EXT

mov INPUT

PEAK

lOOlIlA

PEAK

COMMON

PREAMP OUT

CALIBRATION

m ENABLED m DISPBLED

IEEE 488 INTERFACE

OUTPUT

20OV PEAK

TRIAX

30” MAX

m 90.IlO” q m 180-220”

I x05-l25V ,m. 210-250” q LINE

FUSE 0

SLOWBLDW SO-60Hr AC ONLY

1/4A 90.125V

1,SA ISO-250,’

LINE RATING

25 VA MAX

Figure 2-2. Model 263 Rear Panel

OUTPUT The source output high is available at this trim connector. Source low may also be available here or at the COMMON terminal depending on the configuration of the output.

EXT INPUT This banana plug is used to connect an external supply (up to +200mA) to the Model 263. This external supply is then available at the output of the Model 263 when VOLTS EXT is selected.

COMMON Source output low is always available at this terminal regardless of the configuration of the output.

PREAM,P OUT This terminal along with the COMMON terminal can be used to monitor the voltage drop across a load when the instrument is sourcing current or charge. This terminal can also be used as an external guard source when sourcing AMPS or COUL. PREAMP OUT is inoperative in AMPS V/R, COUL V/R, VOLTS, and OHMS.

CALIBRATION Switch Permanent calibration of the Model 263 can only be done if the CALIBRATION switch is in the ENABLED position.

IEEE CONNECTOR This connector is used to connect the instrument to the IEEE-488 bus. IEEE interface functions are marked above the connector.

LINE VOLTAGE This switch is used to match the instrument to the available line voltage.

LINE FUSE The line fuse provides protection for the AC power line input. The fuse rating must match the line voltage setting.

AC RECEPTACLE Power is applied through the supplied power cord to the 3-terminal AC receptacle.

2.4 CALIBRATOR/SOURCE OPERATION

The following paragraphs will take you through a simple, general, step-by-step procedure to source resistance, voltage, current or charge. The Model 263 can be used to calibrate electrometers and picoammeters, or as a precision source to a load. The following procedure uses a fourfunction electrometer (Keithley Model 617) to demonstrate operation. However, any suitable load or electrometer can be used instead. Using a four-function electrometer for this

demonstration simplifies the procedure and allows the user to measure the actual output of the Model 263. If a suitable electrometer is not available at this time, performing the procedure with an open output will still have instructional benefit.

2-4

GETTING STARTED

2.4.1 Power Up

Check that the instrument is set to correspond to the available line voltage. The line voltage switch is located on the rear panel. If the switch is set to the correct position, connect the instrument to a grounded AC outlet using the supplied power cable and turn on the instrument.

CAUTION If the switch setting does not correspond to the available line power, do not change the switch setting and power up the instrument as the line fuse will probably blow. Instead, proceed to pargagraph 3.2 for the complete power up procedure.

The instrument can be used immediately, however, a one hour warm up period is required to achieve rated accuracy.

2.4.2 Test Connections

For the following procedures, simply connect the output of the Model 263 to the input of the Model 617 Electrometer using the supplied triax cable.

2.4.3 Basic Sourcing Procedure

Configure the Model 617 Electrometer to make unguarded resistance, voltage, current or coulomb rneasuremerits, and select autorange. Perform the following steps to demonstrate the basic sourcing procedure.

Step 1: Select Function

Press the appropriate FUNCTION button (OHMS, VOLTS, AMPS, or COUL). The Model 263 will display the power up default setting of the selected function. For

all functions, except ohms, the display will read zero. On ohms, the actual value of the 1kR resistor will be displayed.

Step 2: Select Range In general, RANGE A upranges the instrument and

RANGE v downranges the instrument.

Step 3: Program Output

There are two methods to set the display to the desired

output reading; the Adjust method and the Keypad method. Try both methods.

Note: OHMS readings cannot be altered since they are fixed resistors

2-5

GETTING STARTED

:>/:::::;

CONTROL

ADJUST A

Figure 2-3. Data Entry Controls - Adjust Method

Adjust Method: (Refer to Figure Z-3.)

1. Position Cursor-Each momentary press of a CURSOR button shows the position of the cursor by briefly flashing a digit segment on and off. To continuously display the cursor position, press SHIFT ON/OFF. Position the cursor on the digit to be changed using the CURSOR 4 and CURSOR b buttons.

2. Adjust Display Reading - Use the ADJUST A button to increase the reading and ADJUST V to decrease the reading. Each momentary press of an ADJUST button increments or decrements the reading by one unit (value is determined by range and cursor position). Polarity of the reading can be changed at any time by pressing the & button.

Keypad Method: (Refer to Figure Z-4.)

- KEYPAD DISABLED

2. Key In Reading - With the cursor positioned at the most significant digit, key in the desired number by pressing the appropriate number button (0 through 9). The rest of the display digits will zero and the cursor will move to the next less significant digit. Key in as many numbers as necessary.

Note: If it is desired to cancel the keyed in reading and return to the reading that was displayed before keypad was enabled, press SHIFT CANCEL. The keypad will disable.

3. Enter Reading With the desired reading displayed, again press KEYPAD/ENTER. The new reading will be entered and the keypad will disable.

Step 4: Go To Operate

To source the programmed parameter to the electrometer, press the OPERATE button. The STANDBY indicator light will turn off and the OPERATE indicator light will turn

on. Note that range changes can be m&ie while in OPERATE.

1. Enable Keypad - Press the KEYPAD/ENTER button to enable the keypad. The keypad indicator light will turn

OIL

2-6

GETTING STARTED

- KEYPAD ENABLED

Figure 2-4. Data Entry Controls - Keypad Method

Step 5: Go To Standby first pressing SHIFT and then the AMPS or COUL but-

ton. The yellow V/R will turn on to indicate the selecTo remove the programmed source from the electrometer, again press the OPERATE button. The instrument will go to standby as indicated by the STANDBY indicator light.

tion of the passive V/R source.

2. If an external source is connected to the EXT INPUT and COMMON terminals, that source will be available at the OUTPUT by pressing SHIFT and then VOLTS. The yellow EXT indicator turns on and the message “USE1

Operating Notes:

V” is displayed.

1. AMPS V/R or COUL V/R may be selected in step 1 by

Z-712-8

SECTION 3

Operation

3.1 INTRODUCTION This section contains detailed information concerning the

operation of the Model 263 from the front panel. The section is arranged as follows:

Power Up Procedure: Describes how to connect the

3.2

instrument to line power and turn it on. Other topics covered include the power up self-tests, power up default conditions and the required warm up period.

Output Characteristics: Provides the user with some

3.3

of the basic output characteristics of the various sources. Includes discussion on current limiting, loading and voltage burden. Understanding these aspects of operation is helpful in obtaining optimum performance from the instrument.

Function and Range Selection: Details how to select

3.4

each sourcing function and how to change ranges. Data Entry: Describes the two methods that can be

3.5

used to program the output reading on the display

of the Model 263. Operate and Zero: Provides details for using these

3.6

two front panel controls. Guard: Describes how to use the Model 263 in the

3.7

guarded output configuration.

3.2 POWER UP PROCEDURE

The information in the following paragraphs describe how to connect the Model 263 to the available line power and turn on the instrument.

3.2.1 Line Voltage

The Model 263 may be operated from either 105.l25V or 210-25OV, 50 or 60Hz sources. A special transformer may be installed (at factory) for 90-1lOV and 180-220V ranges. The instrument was shipped from the factory set for an operating voltage that corresponds to the normally

available lie voltage in your area. To check the line voltage setting, look at the position of the slide switch located on the rear panel (see Figure 3-l). If the switch is in the wrong position, the line fuse will probably have to be replaced with one that has a different rating. Refer to paragraph 8.2 in the maintenance section for the line voltage selection procedure.

LINE

VOLTAGE

Preamp Out: Explains some of the uses for the

3.8

preamplifier output, which are accessible from the rear panel.

3.9

Front Panel Programs: Details information for using the three front panel programs.

3.10 Sourcing Techniques: Outlines how to combine all the operating controls to properly source each source parameter.

3.ll Sourcing Considerations: Provides additional information on temperature compensation, burden voltage and guarding.

Figure 3-1. Line Voltage Switch

3-l

OPERATION

3.2.2 Line Power Connections

Using the supplied power cord, connect the instrument to an appropriate 50 or 6OHz AC power source. The female end of the cord connects to the AC receptacle on the rear panel of the instrument. The other end of the power cord should be connected to a grounded AC outlet.

WARNING The Model 263 must be connected to a grounded outlet in order to maintain continued protection against possible shock hazards. Failure to use a grounded outlet may result in personal injury or death due to electric shock.

3.2.3 Power Switch

To turn on the power, simply push in the front panel POWER switch. Power is on the when the switch is at the inner position. To turn power off, press POWER a second time.

3.2.4 Power Up Self Test

During the power up cycle, the instrument will perform a number of internal tests. Tests are performed on memory (RAM, ROM, and NVRAM). If the tests are successful, the messages “r.r.” and “r.0.” will be displayed briefly. If RAM or ROM fails, the instrument will lock up. If NVRAM fails, the exponent decimal points (i.e. “m.V.“) will blink on and off. See paragraph 8.7 for a complete description of the power up self-test and recommenda-

tions to resolve problems.

Table 3-1. Power Up Default Conditions

Feature Condition

output Function Volts Range 2OOmV Displayed Reading OOO.OOOmV Polarity Positive (+ )

Guard Disabled

Cursor

Keypad Disabled

IEEE Address*

Exponent* Alpha characters

Temperature Compensation On

*These conditions can be changed by front panel programs

to become the new power up default conditions.

Standby

Off, positioned on MSD

3.3 OUTPUT CHARACTERISTICS

To obtain optimum performance from the instrument, it is important to be aware of its basic output characteristics.

Sourcing aspects that affect performance include voltage source, cun‘ent limit, loading, and burden voltage. The

following paragraphs will explain these characteristics.

3.3.1 Voltage Source

The information in this paragraph provides a basic understanding of the output characteristics of the voltage source.

3.2.5 Power Up Configuration

Upon power up, the Model 263 will assume specific operating states. Table 3-1 summarizes the factory default conditions for the unit.

3.2.6 Warm Up Period

The Model 263 can be used immediately when it is first

turned on. Note, however, that the unit must be allowed to warm up for at least one hour to achieve rated accuracy.

3-2

Voltage Source (VOLTS) A simplified circuit of the voltage source is shown in

Figure 3-2. Vs is the voltage setting of the Model 263 and Rs ( < ln) is the output resistance of the source. To deliver the programmed voltage to the load at the accuracy stated

in the specifications, the load must be > 1OOkQ.

When connecting a low resistance load to the output, its effect on the circuit must be considered. The load resistance and the internal resistance of the source (R,) form a voltage divider. Thus, if the load resistor is lOk,

OPERATION

I-_-_--_____-__----_-------~

MODEL 263

Figure 3-2. Voltage Source

approximately 99.99% of Vs will be delivered to the load.

This 0.01% additional error will degrade basic volts ac-

curacy from 0.0175% to 0.0275%. The actual voltage delivered to the load can be calculated as follows:

V, x Ri

vowr =

(R, + R,)

where V

= Voltage delivered to the load

OuT V, = Voltage setting of the 263 R, = Resistance of the load Rs = Output resistance of the source (10)

If the load is <lOOkO, additional error is calculated as follows:

Additional Error (%) =

x 100

Load Resistor + la

/ I

ly handy when running automated test programs over the IEEE-488 bus.

Since internal VOLTS only outputs up to k19.9995 and

+ 19.9995mA, an external source can be used to calibrate instruments that have higher voltage and current requirements. A simplified circuit showing an external source connected to EXT INPUT is shown in Figure 3-3. Maximum inputs for EXT INPUT are 200V peak and lOOmA peak. Staying within these limits will protect the Model 263 from damage.

As with the internal voltage supply, connecting a high impedance device (such as an electrometer) to the output will not result in any loading problems. For low resistance loads and high currents, EXT INPUT circuit resistance (In) should be taken into account. When sourcing voltage through the Model 263, use the following equation to calculate voltage drop through the Model 263:

External Source (EXT INPUT)

EXT INPUT is provided so that the Model 263 can switch select an external source of up to 2OOV and lOOmA. This feature eliminates the need to physically disconnect the Model 263 from the device under test (DUT) in order to connect an external source to the DUT. This is particular-

where V = Voltage drop through the 263.

LXT = Output resistance of the external voltage source. R LoAD = Load resistance. V

Voltage setting of the external source.

E.77 =

3-3

OPERATION

Figure 3-3. External Source

When sourcing current to EXT INPUT, maximum burden voltage of the Model 263 can be calculated as follows:

Maximum Burden V = IQ x I

where I = Current setting of the external source.

3.3.2 Resistance Source

Resistance sourcing is a simple matter of selecting the appropriate resistor. When the Model 263 is calibrated, the resistors are accurately measured and the instrument is adjusted to display those values. Thus, when the instrument is configured to source a resistance, the display will provide the measured reading of that resistor.

On the lGC2,lOGn and lOOGO ranges, the resistor reading on the display will change as the instrument warms up,

and as ambient temperature changes occur. These resistors have a high negative temperature coefficient (TC). As the temperature of the resistor rises, its resistance decreases. The display is able to track the output resistance because

a TC profile for each of these three resistors is established when the instrument was calibrated. In effect, the instru-

ment “knows” what the output resistance is at all operating temperatures. This temperature compensation feature can be disabled by front panel Program tc (see paragraph

3.9.3). With temperature compensation disabled, the instrument will display the resistor reading that was measured (during calibration) when the internal temperature approximated the normal operating temperature. See paragraph 3.11.1 for more information on temperature compensation.

3.3.3 Current and Charge Source

The Model 263 provides two methods to source c&rent

for the current and charge functions. When the AMPS or COUL button is pressed, the active current source is selected. When SHIFT AMPS or SHIFT COUL is pressed, the passive (V/R) source is selected.

Active Current Source (AMPS) Figure 3-4 shows a simplified schematic of the active cur-

rent source (AMPS). With this method, the output current remains at the programmed level regardless of the load resistance, as long as the compliance voltage of f 12V is not exceeded. Compliance voltage is the maximum voltage that can appear across the unknown with the programmed current still being sourced.

3-4

OPERATION

---------------------------------------

MODEL 263

R, =lkRto 1OOGR

dvv

Figure 3-4. Active Current Source (Unguarded)

Example-Model 263 configured to output 1mA to a 5kQ load. The value of V, is determined by the programmed current level and the feedback resistor (R,). On the 1mA range the 1Okn feedback resistor is used. Thus, V, is 1OV (10kQ x ImA). The voltage drop (V,) across the load (RLOAO) is 5V (1mA x 5kR).

If the voltage compliance limit is surpassed, the OPERATE light will flash on an off indicating that the instrument cmnot source the programmed current level to the load.

Example-Model 263 configured to output 1mA to a 20kR load. Sourcing lm.4 to a 20kO resistor would result in a V, of 20V (1mA x 20kQ However, V0 will limit

(OPERATE light flashing) at approximately 12V which is the compliance limit, and the resulting output current wiIl be less than ImA.

To prevent the voltage limit condition (flashing OPERATE

light) make sure that the product of the programmed out-

put current times the load resistance is less than 12V

(I x R < 12V).

Notes:

1. Voltage limit will never occur when sourcing to a feedback ammeter since the burden voltage of this device

is so low. The burden voltage, typically 1mV or less, is the voltage drop seen across the input of the elec-

trometer

or picoammeter.

2. The compliance voltage is a minimum of * 12V, but will

probably approach *15V before the OPERATE light flashes.

Passive Current Source (AMPS V/R) Figure 3-5 shows a simplified schematic of the passive cur-

rent source. The values of R and V, are dependent on the selected range and output setting. The values of R and V, we selected such that the programmed current will flow in the circuit when the output is connected to a virtual ground. Thus any device, whether it be a resistor or an electrometer, will cause a loading error to some degree.

Example-With the Model 263 configured to output 1mA on the 2mA range, the value of R will be 1kR (see Table 3-4) and V, will be at 1V (ImA x 1kR). If the output of the Model 263 is shorted, ImA will flow in the circuit. If the output is connected to a 1kQ load, only 0.5mA will flow in the circuit.

In this simple series circuit, it is obvious that the only way to sowce current at the programmed setting is to connect the output to a virtual short. This is why the output of the passive current source should only be connected to a device (picoammeter) that has a low burden voltage. Burden voltage is the voltage drop seen across the device. The current source accuracy specifications, excluding offset, include the error introduced by devices that have a

1OOpV burden voltage. The additional error caused by devices that have more than 1OOpV of burden voltage can

be calculated (see paragraph 3.11.2).

Calibrating an electrometer that has a burden voltage specification of > 1OOpV is not a problem as long as the input offset voltage of the input amplifier can be adjusted. Nulling out the offset voltage of the picoammeter input amplifier can reduce the burden voltage to almost zero.

3-5

OPERATION

I I I

R =ikn to IOOGR

Figure 3-5. Passive (V/R) Current Source

Charge Source The Model 263 outputs charge by sourcing a specific cur-

rent level for one second. This technique is based on the following fundamental charge equation:

Q=Ixt

where Q = Charge in coulombs I = Current in amperes t = Time in seconds

If the Model 263 is programmed to output a charge of

lo&, it will actually output lOpA for one second. Thus

the fundamental difference between the current function

and the charge function is the time duration of the out-

put current. COUL uses the active current source, while

COUL V/R uses the passive current source.

3.4 FUNCTION and RANGE SELECTION

The following paragraphs provide the information needed to select function and range.

3.4.1 Function Selection

Ohms-To select the ohms function, simply press the OHMS button. The OHMS light will turn on.

Volts-To select the volts function, simply press the VOLTS button. The red VOLTS indicator will turn on.

EXT INPUT-To select EXT INPUT first press SHIFT and then press VOLTS. The yellow EXT indicator will turn on.

AMT-To select the active current function, press AMPS. The red AMPS indicator will turn on.

AMPS V/R-To select the passive (V/R) current function, first press SHIFT and then press AMPS. The red AMPS light and the yellow V/R indicator will turn on.

COULOMBS-To select the active charge function, press COUL. The red COUL indicator will turn on.

COULOMBS V/R-To select the passive (V/R) charge function, first press SHIFT and then press COUL. The red COUL indicator and the yellow V/R light will turn on.

Note: Any time a function button is pressed, the output will go to the standby condition.

3.4.2 Range Selection

The RANGE buttons are used to change ranges. Each momentary press of RANGE A upranges the display to the next highest range, while RANGE 7 downranges to the next lowest range. These buttons have auto-repeat capability. That is, holding in a RANGE button will cause the instrument to continually uprange (A) or downrange

(v) until the largest or smallest range is reached.

3-6

OPERATION

Figure 3-6. Data Entry Controls - Adjust Method

Available ranges depend on the selected function and are listed in the specifications. Note that the ohms ranges in the specifications list the nominal resistance values. The actual values of the resistors are displayed by the instrument.

As a general rule, always select a range that meets the best accuracy and resolution requirements.

Output Response-When a range button is pressed while on any function, except OHMS, the output will immediately go to zero for a half second and then ramp to the new output level in <‘/I second. In OHMS, output changes are immediate.

3.5 DATA ENTRY

The output value of all functions on a given range, ex-

cept ohms, can be modified. There are two methods to change the display to the desired ou

just method and the Keypad metho f

depends on your preference, but when making minor changes to the displayed reading, the Adjust method is

ut reading; the Ad-

The method to use

KEYPAD DISABLED

probably faster. Keypad entry is the best choice when an entirely new reading is going to be entered.

3.5.1 Adjust Method

Refer to Figure 3-6 and perform the following procedure to change the display reading using the adjust method:

1. Position the cursor on the digit to be changed using the CURSOR buttons.

Cursor position is identified by a briefly flashing digit segment whenever a CURSOR button is momentarily pressed. Each momentary press of CURSOR 4 moves the cursor one digit to the left, and each press of CURSOR ) moves the display one digit to the right.

The CURSOR buttons have auto-repeat capability. That is, holding in a CURSOR button will cause the cursor to scroll from left-to-right 0) or from right-to-left (4).

Note: The cursor can be turned on by pressing SHIFT ON/OFF. A segment of the selected digit (indicating cursor position) will flash continuously. To turn the cursor off, again press SHlFI ON/OFF. The cursor will also disable anytime a function button is pressed.

3-7

2. Adjust the display reading using the ADJUST buttons.

Enable the keypad by pressing KEYPAD/ENTER.

Each momentary press of the ADJUST A button will increment the reading by one unit (value is determined by range and cursor position). For example, with the instrument on the 2OmA range and the cursor ositioned on the thousanths digit (second digit from

tl?e right), each press of ADJUST A will increment the reading by &A. Conversely, each momentary press of ADJUST V decrements the reading by one unit. The exception to this rule is the least significat digit that changes by five units when an ADJUST button is pressed. The ADJUST buttons also have auto-repeat capability. That is, holding in an ADJUST button will cause the reading to increment (A) or decrement (V) automatically.

Notes:

1. Polarity of the reading can be changed by pressing the * button.

2. Polarity of the reading will also change when the display

is adjusted past zero.

3. The display reading cannot be adjusted past the liits

of the range. However, range changes can be made at any time.

4. If the instrument is in OPERATE, the output will change

as the display reading changes.

3.5.2 Keypad Method

Refer to Figure 3-7 and perform the following procedure to enter a reading on the display:

The KEYPAD light will turn on and a segment of the most significant digit will flash to indicate the position of the cursor. Key in the reading using the numeric data entry buttons.

With the cursor at the most signficant digit, key in the desired number by pressing the appropriate number button (0 through 9). The rest of the display digits will zero and the cursor will move to the next less significant digit. Key in as many numbers as necessary. The least significant digit can only be a 0 or a 5. Keying in 0 to 4 will set that digit to 0, and keying in 5 to 9 will set it to 5.

Enter the keyed in reading by again pressing KEYFAD/ ENTER.

The new reading will be entered and keypad will

disable. Prior to this step, the display reading

was

changed, but the output was not affected.

Notes:

1. Press the * button to change the polarity of the display reading.

2. Range changes can be made with the keypad enabled.

3. A keyed in reading can be cancelled by pressing (SHIFT) CANCEL. The keypad will disable and the display will return to the reading that was on the display before keypad was enabled.

4. Pressing any function button is the same as pressing (SHIFT) CANCEL (see Note 3), however, the inshw

ment will go to (or stay at) the selected function.

3-8

IKEITHLEY 263 CALIBRATOR i SOURCE

OPERATION

Figure 3-7. Data Entry Controls- Keypad Method

3.6 OPERATE and ZERO The following paragraphs contain information on the

OPERATE and ZERO features.

3.6.1 Operate The OPERATE button toggles the output between stand-

by and operate. In standby, yellow STANDBY light on, for all functions except COUL and COUL V/R, the 100Gn resistor is placed on the output. In COUL and COUL V/R, zero coulombs, on the range selected, is placed on the output.

In the coulombs function, the instrument will only stay in operate for approximately one second each time

the

OPERATE button is pressed.

KEYPAD ENABLED

3.6.2 Zero

The ZERO button toggles the display between the existing reading and zero. This provides an easy method to source zero in order to cancel offsets and test lead resistance. The output must be set to OPERATE in order to source zero.

On all functions except OHMS, particularly on the most sensitive ranges, the Model 263 has a very slight offset that is added to the output. The maximum offset output on each function/range is included in the accuracy specifcation. This offset is present whether the instrument is sourcing zero or full range.

When zero is sourced to an electrometer or picoammeter, the offset of the Model 263 will be measured. The electrometeripicoammeter can then suppress the offset so that it also reads zero. The readings on the electrometer or picoammeter will then accurately track the displayed output of the Model 263.

3-9

To achieve rated accuracy when sourcing lkn or lOk0 to an electrometer, zero must be used to cancel ZERO OFFSET and test lead resistance. When’zero ohms is sourced to an electrometer, the resistance measurement will include these resistances. The electrometer can then suppress the reading so that it also reads zero.

put high and the inner shield the same, no leakage current can flow. The leakage from the guarded inner shield to low (through R, and C,) is of no consequence since the current is supplied from the guard source (V,) and not from output high. More information on the principles of guarding is contained in paragraph 3.11.3.

The procedures to zero out offset and test lead resistance are included in the sourcing techniques in paragraph 3.10.

3.7 GUARD In general, the purpose of guarding is to eliminate leakage

resistance and capacitance that exist between output high and output low. In the unguarded configuration (see Figure 3-S), leakage occurs between the center conductor

(HI) and the inner shield (LO) of the output t&w cable.

This leakage (through R, and C,) may be enough to

adversely affect the output level and response time of the

source.

In the guarded configuration (see Figure 3-9), output low is connected to common, allowing a guard potential (equal to the potential at ouput high) to be connected to the inner shield of the cable. With the voltage potential on out-

The Model 263 supplies the guard drive for AMPS and COUL. However, the user must supply the guard drive for AMPS V/R, COUL V/R, OHMS and VOLTS. When GUARD is enabled with any of these functions selected, the inner shield of the triax connector is floating unless a guard drive is supplied by the user.

Guard Enable-To place the output of the Model 263 in a guarded configuration press SHIFT GUARD. The yellow GUARD light will turn on. Pressing SHIFT GUARD a second time will disable guard and return the output to the unguarded configuration.

Whenever GUARD is enabled, source output low is physically connected to the COMMON terminal. Therefore, always use a separate cable to connect COMMON of the Model 263 to common of the device under test (DUT).

3-10

Figure 3-8. Unguarded Circuit

OPERATION

r------ r-----I I

’ PR ’ PR ; ou ; ou

I I I I

-----------------J

MODEL 263

MODEL

263

(GUARD ENABLE)

Figure 3-9. Guarded Circuit Figure 3-9. Guarded Circuit

3.7.1 Guarded Ohms

WARNING

Hazardous voltage may be present on the in-

ner shield of the OUTPUT connector when sourcing guarded ohms. A safety shield (outer shield of the supplied triax cable) connected to

earth ground should be used.

Guarding is recommended for resistances zlOOM0. The unguarded and guarded output configuration for ohms is shown in Figure 3-10. With guard enabled, output low is physically disconnected from the inner shield of the OUTPUT connector on the rear panel of the Model 263. This allows guard drive to be connected to the inner

shield. In OHMS, guard drive (the inner shield of the t&x connector and cable) must be provided by the external DUT.

Most electrometers have an output connector that provides a guard drive. Some electrometers (such as the Keithley Model 617) have the capability to reconfigure its

input (through means of a switch) and internally connect

the guard drive to the inner shield. With this capability,

connecting the Model 263 to the electrometer is a simple

INNERSHIELD INNERSHIELD

“G=“OUT “G=“OUT

matter as shown in Figure 3-11. For electrometers whose input cannot be reconfigured, an input adapter will be required. The objective of the adapter is to connect the guard source of the electrometer to the inner shield (guard) of the Model 263. Two such input adapters are available from Keithley. The Model 6167 is used with Keithley Model 614 Electrometer, while the Model 6191 is used with the Keithley Model 619 Electrometer. Figure 3-12 shows how the Model 263 is connected to an electrometer (Model 619) using an input adapter (Model 6191). Note that in Figures 3-11 and 3-12 source low is routed to the electrometer using a separate banana plug cable. This cable eliminates the need to route source low through earth ground connections that may have higher resistance.

In some electrometers there is a resistor (typically 100Cl or lk0) connected between common and low (see Figure 3-11). In guarded ohms this resistor is in series with the output resistor of the Model 263. In this situation, never use guard to source c100MO to the Model 617 and

110MIl to the Model 614. In the unguarded configura-

tion, source low is routed directly to meter low.

Table 3-2 summarizes the techniques to source guarded ohms to Keithley electrometers.

3-11

OPERATION

COMMON

A. UNGUARDED

MODEL 263

~_____________-, I

I I

_--_-----------

OUTPUT t

B. GUARDED

Figure 3-10. Ohms Output Configurations

MODEL 617 ELECTROMETER

I I

I I I

GUARD

I I I

, I I I

Figure 3-11. Sourcing Guarded Ohms to Electrometer that has a Selectable Guarded Input

3-12

t--------7 I

n, ,101 I

TRIAX

TR,Axr ______ ----__--__

OPERATION

__.” ._

i%u+> !

I _-______ J

MODEL 263

(GUARD ENABLED)

1 I I

I : UNGUARDED GUARDED ’

L_ -__ __ _ ___ __I

MODEL 6191 ADAPTER u3

BANANA CABLE

p-- i

r v 4 INPUT

------_-___

MODEL 619 ELECTROMETER

BANANA CABL

,!a

.iF

Figure 3-12. Sourcing Guarded Ohms to Electrometer Using an Input Adapter

3-13

OPERATION

Table 3-2. Sourcing Guarded Ohms to Keithley Electrometers

Model No.

602

610C

614 616

617

619

Selectable Guarded

Input Available?

Yes None

NO NO 6167

Yes None

Yl?S

Required Input

Adapters* (Keithley Model No.)

4804, CS-115

None

Guarded Ohms

Measurement Range

All All

> 100Mn

All

> 1OMQ

All

Zonnection

Scheme

Figure A

Figure B Figure C Figure D

Figure E

Figure F

OPERATION

3.7.2 Guarded Amps and Coulombs

NOTE

The following discussion on guarded amps also applies to the Coulombs function.

The unguarded and guarded output configurations for

amps is shown in Figure 3-13. With guard enabled, output low is disconnected from the inner shieldof the OUT PUT connector, and the internal guard drive is connected to that inner shield. Output low can be routed to the outer shell of the output connector b installing the shorting link. However, installing the l&connects output low to chassis ground, eliminating the floating capability of the instrument.

There is no need to use p”d if the Model 263 is sours-

mg current to a feedbac plcoammeter as ths cucmt IS already guarded. Figure 3-14 shows the Model 263 connected to a feedback picoammeter. Because the voltage drop (burden voltage) axoss the input of the picoammeter

is very low (typically <lmV), the voltage on HI and LO are are virtually identical. With the same voltage potential, no leakage current can flow.

The Model 263 can be used in the guarded configuration

if it is connected to a shunt picoammeter. The shunt or

ation is onl i%ezc?E%Keithley h&dels 602 and 610C. The input of a shunt picoammeter is actually configured as a

shunt electrometer voltmeter. The guarding technique is similar to the one used for sourcing ohms to an electrometer using an input adapter. Both the Keithley Models

available on older elec-

6191 and 6167 Input Adapters can be used with the Model

602. Figure 3-15 shows how the Model 263 is connected to a shunt picoammeter (Model 602 set for ‘NORMAL” amps) using an input adapter (Model 6191). Notice that the guard cable from the input adapter is not connected to the electrometer since guard voltage is provided by the

Model 263.

Guarding is recommended when sourcing current or charge to ahigh impedance load. Arecommended guarding method is shown in Fi put high is guarded all t

e 3-16. With this method out-

e way to the load.

8”

In AMPS and COWL, guard drive is also available at the PREAMP OLJT terminal on the rear panel. Guard drive is available at that terminal in both the guarded and unguarded configurations. Figure 3-17 shows an application for the external guard. This configuration makes it possible to source current to a particular resistor (Rl) without disconnecting other components (R2 and R3) in the resistor network. As configured, all of the output current will flow through Rl. This is because virtually the same voltage potential exists on both sides of RZ. In reality, a slight voltage difference exists because of the voltage offset of the preamplifier. In most situations, the resultant current through R2 is insignificant. The current that flows from PREAMP OUT through R3 is of no consequence.

In AMPS V/R and COLJL V/R, guard drive is not available at I’REAMP OUT. Since AMPS V/R and COUL V/R are usually used to calibrate electrometers, grounding is not needed. If sourcing AMPS V/R or COUL V/R to a load, a guard drive will have to be obtained from an external device.

3-15

OPERATION

PREAMP

OUT

PREAMP

OUT

263

CURRENT

SOURCE

A. UNGUARDED

GUARD

263

CURRENT

SOURCE

3-16

B. GUARDED

Figure 3-13. Amps/Coulombs Output Configurations

; PREAMP

FEEDBACK PICOAMMETER

MODEL 263

OUTPUT ’ i INPUT

GUARD DISABLED

~_______________________

Figure 3-14. Sourcing Amps to a Feedback Picoammeter

OPERATION

,__-__-_______.

MODEL 263

(GUARD ENABLED,

t------------

BANANA CABLE

SHUNT PICOAMMETER

(MODELS 602,)

.-__- ____ ----,

I I I I

Figure 3-15. Sourcing Guarded Amps to a Shunt Picoammeter Using an Input Adapter

3-17

OPERATION

_--~_-------_----------~~~~~----~. I I

I I I I

; GUARD , ENABLED

‘--_____-_--_-_-_-_-_____________1

MODEL 263

GUARD

Figure 3-16. Guarding for High Impedance Load

I I I I

No CONNECTlONS

,_--___-_____--___--_____I

I I I I I I I I

.-__--______----____-----

MODEL 263

Figure 3-17. Using PREAMP OUT Guard

OUTPUT

I I

GUARD(VG)

3-18

OPERATION

3.7.3 Guarded Volts Guarding volts is unnecessary, however, the output con-

figuration does change when GUARD is enabled (see Figure 3-18).

3.8 PREAMP OUT When sourcing current or charge, the PREAMP OUT and

COM terminals on the rear panel of the instrument can be used to monitor the v&age drop across a load. Figure

3-19 shows

how

PREAMP OUT is configured with the

CUTPUl

load. The preamplifier has a Xl gain, thus the voltage potential at I’REAMP OUT is the same voltage dropped across the load. Using buffered PREAMP OUT minimizes

loading effects that may occur if voltages were monitored

at the load.

PREAMP OUT can also be used as an external guard

source when sourcing current or charge. See paragraph

3.72 for details.

Note: Maximum current draw from PREAMF OUT is 5mA

and maximum load capacitance is 10nF.

A. UNGUARDED

Figure

3-18.

B. GUARDED

Volts Output Configuration

3-19

OPERATION

r__---__-______-___------~ I

MODEL 263

Figure 3-19. Using Preamp Out to Monitor Load Voltage

3.9 FRONT PANEL PROGRAMS

Three programs are available from the front panel: Program IEEE is used to check/change the IEEE-488 primary address of the instrument, Program dISP toggles the

display reading from engineering units (e.g. mV) to scientific notation (e.g. -6), and Program tc checks/changes the status of the temperature compensation feature.

I I I

LOAD

2. To change the displayed address value, use the ADJUST buttons. ADJUST A increments the value while ADJUST Y decrements the value.

3. To enter the displayed primary address, simply press MENU again. The instrument wiIl rehxn to normal operation and the programmed address value will be stored in memory. Thus, the instrument will power-up to the programmed primary address.

In general, a program is selected with the MENU button, modified by the ADJUST buttons, and entered again by pressing the MENU button. Detailed instructions for us-

ing these front panel programs are contained in the following paragraphs.

3.9.1 Program

IEEE

The Model 263 is shipped from the factory set for an IEEE-488 primary address of 8. This program allows the user to check and/or change the address of the IEEE-488 interface. The interface can be set to any primary address from 0 to 30. Detailed information on the IEEE-488 bus is provided in Section 4. Perform the following steps to use this program:

1. Press the MENU button until the current primary address of the interface is displayed. For example, if the

primary address is 8, the following message will be

displayed:

IEEE 8

3.9.2 Program dlSP This program is used to select the alternate display mode.

The Model 263 will display readings in engineering units or scientific notation. For example, a value of 1OOmV in the engineering units display would read lOO.OOOmV. The same value displayed in scientific notation would read

1.00000 -1. Perform the following steps to use this program:

1. Press the MENU button until the current display mode is displayed. If the engineering units display is currently selected the following message will be displayed:

dISP u

If the scientific notation display is currently selected, the following message will be displayed:

dISP -6

3-20

OPERATION

2. To display the alternate display mode, press any ADJUST button. These buttons toggle the display between the two modes.

3. To enter the displayed mode, again press the MENU button. The instrument will return to normal operation and the programmed display mode will be stored in memory. Thus, the instrument wiIl power-up to the

programmed display mode.

3.9.3 Program tc

This program is used to check and/or change the status

of the temperature compensation feature of the Model 263.

Temperature compensation is discussed in paragraph

3.11.1. Perform the following steps to use this program:

1. Press the MENU button until the status of the

temperature compensation is displayed. If temperature compensation is enabled, the following message will be displayed:

tc 1

If temperature compensation is disabled, the follow-

ing message will be dislayed:

tc 0

2. To change the displayed status of temperature compensation press any one of the ADJUST buttons. These two buttons toggle the display between 1 and 0 (on and off).

3. To enter the displayed status of temperature compensation, again press the MENU button. The instrument will return to normal operation. Unlike the other programs, programming temperature compensation for 0 (off) will not be remembered on the next power-up. On power-up, temperature compensation will always be enabled (1).

3.10 SOURCING TECHNIQUES

Using the front panel controls has already been discussed in detail in previous paragraphs. Thus, this section will not repeat the details of performing each task required to source a particular parameter. Detailed information on function selection, range changes, data entry, guard, and zero can be found in paragraphs 3.4 through 3.8. The objective of this section is to show how all the operating tasks combine to properly source each parameter.

3.10.1 Connections

The rear panel OUTPUT connector is a Teflon@ -insulated 2-lug triax receptacle intended for output signals from the Model 263. In the tion, the center terminal is high, the inner shield is low, and the outer shell is connected to instrument chassis ground (see Figure 3-20). In the guarded configuration, the inner shield is used for the guard potential and source low is connected to the COMMON terminal. With the

shorting link installed, source low is routed to the outer

normal

unguarded output configura-

OUTPUTHIGH

OUTPUT LOW

CHASSlSf

GROUND

A. UNGUARDED

(GUARD DISABLED)

37-

COMMON

6-O

OUTPUT HIGH

GUARD

CHASSIS

GROUND

B. GUARDED

OUTPUT LOW

COMMON

(GUARD ENABLED)

Figure 3-20. Output Connector Configuration

3-21

OPERATION

shell of the OUTPUT connector. Paragraph 3.7 explains

how to use the guarded output of the Model 263.

For equipment that does not use triax input connectors, adapters may be needed to connect an input connector to a female triax output connector. To mate a BNC input connector to a triax output connector, attach a male BNC to a female triav adapter (Keithley Model 4804) to the BNC connector. The supplied triax cable can then be used to make the connection. To mate a UHF input connector to a triax output connector, attach a UHF-to-BNC adapter

(Keithley PIN CS-115) to the UHF input connector, and attach a male BNC to female triax adapter to the BNC connector. The triax cable can then be used to make the connection.

WARNING

The maximum applied common-mode voltage (the voltage between output low and chassis ground) is 350V peak. Exceeding this value may create a shock hazard and cause damage to the instrument. If using the Model 6167 or 6191 input adapter, any applied common-mode voltage also exists between output low and Its chassis.

sourcing, simply connect the output of the source to the input of the electrometer as shown in Figure 3-21. Adapters for non-triax input connectors are described in paragraph 3.10.1. Guarded connections should be used for sourcing >lOOMO. Required guarding schemes are described in paragraph 3.7.1.

2. Select the ohms function by pressing the OHMS button.

3. If sourcing lkbl or lOkQ, perform the following steps to cancel ZERO OFFSET test lead resistance.

A. If autoranging is not available, set the electrometer

to its lowest ohms range.

B. Press the ZERO button on the Model 263. The

display will read zero.

C. Press OPERATE on the Model 263. Less than la will

be sourced to the electrometer. The measured reading on the electrometer will be the test lead resistance and ZERO OFFSET.

D. Zero the display of the electrometer using its zero

or suppress feature.

E. Again press ZERO to source the lka resistor. The

reading on the electrometer will exclude test lead resistance and internal resistance of the source.

4. Use the the RANGE buttons to select any one of the

available resistors.

3.10.2 Sourcing Ohms

Perform the following procedure to source ohms to an electrometer. Make sure that the electrometer is set to measure ohms and on autorange, if available. Otherwise, change ranges as required to keep the electrometer on the optimum range.

1. With the Model 263 in standby, connect the source to the electrometer. Generally, unguarded connections can be used when sourcing 5 lOOM% For unguarded

MODEL 263 ELECTROMETER

__-__- ______ I I

OUTPUT

I 4 I I L------- ___I

I I I I

I TRIAXCABLE I I

-----------I I

I L - - - - _ - - _ - -’

INPUT

I I I I

Figure 3-21. Unguarded Sourcing to Electrometer

3-22

Notes:

1. With the instrument in Operate, use the ZERO button to source zero ohms. This button toggles the output between zero and the selected output resistor.

2. In STANDBY, the lOOGO resistor is sourced.

3. To achieve rated accuracy, do not apply more than 20V across the lk0 through lOG0 resistors, or 1OOV across the lOOGo resistor.

4. Additional specifications for OHMS are contained in Table 3-3.

Resistor Temperature Coefficient-The resistor temperature coefficient (TC) given in the OHMS specifications are the corrected TCs of the resistors. That is, the TCs with the Temperature Compensation feature enabled. With Temperature Compensation enabled, the Model 263 updates the display to correspond to the actual resistor value. The Model 263 does not change or correct the actual value of the resistor, it only reports the value at a given temperature. The temperature coefficient of the GO resistors with Temperature Compensation disabled, (no correction) is as follows:

lOOGo: 800 ppmi”C

1OGQ: 170 ppm/“C

1GQ: 170 ppmi”C

Table 3-3. Additional Ohms Specifications

Voltage

Range

kil

kfi

100

1Mll

10Mil

1OOMfl

1GO

lOGil

lOOGO

Coefficient

(ppm/V)

3 1 1 1

3 5

100

Maximum Voltage

across Resistance

2ov 3ov 5ov

5ov 250V 250v 25ov 250v 250v

3.10.3 Sourcing Volts The Model 263 can source up to + 19.9995V. By connecting

an external voltage source to EXT INPUT, up to i2OOV

peak can be made available at the output. The voltage source can be used to calibrate electrometers, or connected to a load. If sourcing to an electrometer, set it on autorange, if available. Otherwise, change ranges as required to keep it on the optimum range. Perform the

following procedure to use the voltage source:

1. With the Model 263 in STANDBY, connect the source to an electrometer to be calibrated or to a load. Guarded connections are not necessary when sourcing volts.

A. If an external source is to be used, connect its out-

put to the EXT INPUT terminals of the Model 263

as shown in

Figure 3-22.

WARNING A common-mode external voltage may be applied to the output connector. Common-mode voltage is the voltage between output low and chassis ground. A shock hazard exists if common-mode voltage exceeds 30V.

B. To source voltage to an electrometer, connect the

output of the Model 263 to the input of the electrometer as shown in Figure 3-21. If the electrometer does not have a triax input connector, an adapter will be needed (see paragraph 3.10.1.).

C. To source voltage to a load, connect source HI to one

side of the load and source LO to the other side as shown in Figure 3-23.

2. Select the volts function as follows: A. For normal volts, press the VOLTS button. The red

VOLTS indicator will turn on.

B. For external volts, fist press SHIFT and then press

VOLTS. The yellow VOLTS indicator will turn on and the message “USEr V” will be displayed. Proceed to step 5.

3. For normal volts, select the appropriate voltage range using the RANGE buttons.

4. For normal volts, enter the desired voltage reading on the display using the Adjust method or the Keypad method. In general, the Adjust method consists of positioning the cursor on the digit to be changed using the CURSOR buttons, and adjusting the display reading

using the ADJUST buttons. The Keypad method con-

sists of enabling the keypad by pressing KEYFAD/

ENTER, keying in the reading using the numeric data buttons, and entering the reading by again pressing KEYT’ADIENABLE. Details on data entry can be found in paragraph 3.5.

3-23

If the output is connected to an electrometer, offset error of the source can be cancelled as follows:

A. Press the ZERO button on the Model 263. The

display will read zero volts.

B. Press OPERATE on the Model 263. Zero volts will

be sourced to the electrometer. The measured reading on the electrometer will be the offset of the

source.

C. Zero the display of the electrometer using zero or

suppress. Subsequent voltage measurements will exclude offset error.

D. Press OPERATE on the Model 263 to place it in

standby.

E. Press ZERO on the Model 263 to display the pro-

grammed voltage setting.

6. When ready to output the displayed voltage, press OPERATE.

Notes:

1. While in OPERATE, the ZERO button toggles the output between zero volts and the programmed voltage setting.

2. Setting the instrument to STANDBY removes the voltage source from the output and places the 100Gn resistor on it.

3. For best accuracy, select a range that is closest to the desired output level.

4. To achieve rated accuracy, load resistance must be

> 1OOkQ and load capacitance must be < 1000pF.

3.10.4 Sourcing Amps and Coulombs The Model 263 can source current up to + 19.9995mA and

charge up to i19.9995pC configured as an active source (AMPS or COUL) or as a passive source (AMPS V/R or COUL V/R). The difference between the active and passive (V/R) source is explained in paragraph 3.3.1. Perform the

following procedure to source amps to a picoammeter or

load, and coulombs to a coulombmeter. If sourcing to a picoammeter or coulombmeter, make sure it is on autorange, if available. Otherwise, change ranges as required to keep the meter on the optimum range.

1. With the Model 263 in standby, configure the equipment as follows:

A. To source current or charge to a feedback meter, sim-

ply connect the output of the Model 263 to the input of the meter as shown in Figure 3-22. If the meter does not have a triax input connector, an adapter will be needed (see paragraph 3.10.1). Guarding is

not necessary when sourcing current or charge to a feedback meter.

B. Sourcing current or charge to a shunt meter may re-

quire guarding because of the relatively high burden

voltage (typically 400mV). See paragraph 3.7.2 for

guarding methods. If guarding is not going to be used, connect the source to the meter as described in step A.

C. To source current to a load, connect the output of

the Model 263 to the load as shown in Figure 3-23. If sourcing to a high impedance load, cable leakage currents may be large enough affect load current. In

3-24

IEL 263

MOD

._-__--_-___-_

EXTERNAL

VOLTAGE

Q-3 IFITF

-___I

I I

-_--___

Exr INPUT

Figure 3-22. Connecting External Voltage Source to Model 263

OPERATION

this situation guarding will be required (see paragraph

3.7.2).

2. Select the amps or coulombs function as follows: A. Select an amps function as follows:

a. For AMPS, press the AMPS button. The red

AMPS light will turn on.

b. For AMPS V/R, first press SHIFT then AMPS.

The red and yellow indicator lights will turn on.

B. Select coulombs function as follows:

a. For COUL, press COUL. The red COUL indicator

will turn on.

b. For COUL V/R, fist press SHIFT then COLJL.

The red and yellow indicators will turn on.

3. Select the desired range using the RANGE buttons.

4. Enter the desired current reading on the display using

the Adjust method or the Keypad method. In general, the Adjust method consists of positioning the cursor on the digit to be changed using the CURSOR buttons and adjusting the display reading using the ADJUST buttons. The Keypad method consists of enabling the keypad by pressing KEYPAD/ENTER, keying in the reading using the numeric data buttons, and entering the reading by again pressing KEYPAD/ENTER. Details on data entry can be found in paragraph 3.5.

5. If the current output is connected to a pica-eter, the

offset current of the source can be cancelled as follows.

(Cancelling offset of the coulombs function is not

recommended). A. Press the ZERO button on the Model 263. The

display will read zero amps.

B. Press OPERATE on the Model 263. Zero amps will

be sourced to the Model 263. The measured current on the picoammeter will be the offset current.

C. Zero the display of the picoammeter using zero or

suppress. Subsequent current measurements will exclude the offset current.

D. Press OPERATE on the Model 263 to place it in

standby.

E. Press ZERO on the Model 263 to display the pro-

grammed current setting.

6. When ready to output the displayed current or charge, press OPERATE. If in the coulombs function, charge

will source for approximately one second.

3. COULOMBS specifications require a three-second measurement interval or shorter to achieve the stated specifications. This is due to current offsets that are dependent on the leakage current of the Model 263 in COUL and with the burden voltage of the unit under test. Since charge is equivalent to Current x Time, the longer the leakage or offset current flows the greater the additional charge that will be effectively delivered to the unit under test. Below is a table listing the additional offset per second that must be added to the specifications for tests requiring measurement intervals greater than three seconds.

Additional offset for

each second over three seconds

Range

2opc

2oopc

2nC

20nC

200nC

20 UC

Amps V/R Amps

- -

100fC 100fC

IPC

1opc

1oopc

1nC

1PC

1opc

1oopc

1nC

For example, if 1nC is to be output and the measurement interval is 10 seconds, the additional offset that must be added is:

1OOfC x (10 seconds - 3 seconds) = 700fC

Generally, COUL V/R will yield better performance on the 2OpC and 2OOpC and COUL above these ranges.

MODEL 263

----------7

Notes:

1. While in OPERATE, the ZERO button toggles the output between zero amps and the programmed current.

2. Placing the Model 263 in STANDBY: A. AMPS - Places the 100GQ resistor on the output. B. COUL Places zero coulombs on the output. A small

charge may be measured by the electrometer because of the offset leakage current of the range. Zero check the electrometer to bleed off the charge before sourcing coulombs.

I___

Figure 3-23. Sourcing to a Load

3-25

OPERATION

3.11 SOURCING CONSIDERATIONS

3.11 .l Temperature Compensation

The lG62, lOGIl and lOOGO resistors have a high negative temperature coefficient (TC). As the temperature of the resistor rises, resistance decreases. Thus, all functions/ ranges that use these resisitors are affected. Ordinarily, the change in resistance may be enough to significantly affect the output of functions/ranges that use these resistors. However, the temperature compensation feature of the Model 263 compensates for this temperature change. Table 3-4 lists the functions/ranges that are temperature compensated.

Table 3-4. Temperature Compensated Functions/

Ranges

Function Ohms

Amps Coulombs

Ranges

lG0, lOGi?, lOOGO ZnA, ZOOpA, ZOpA, 2pA 2nC, 2oopc, 2Opc

to l.OOlV in order to source 1nA or 1nC. If the resistance changes to 1.0007GQ the voltage source will change to

1.0007V to maintain the output at 1nA or Inc. Always knowing the actual output resistance allows the instrument to adjust voltage accordingly.

If temperature compensation is disabled, the instrument will use the “hot” resistance value to calculate the voltage needed to source the programmed current or charge.

3.11.2 Burden Voltage

Burden voltage is a major consideration when sourcing passive (ViR) current or coulombs to an electrometer or picoammeter. Ideally, the input voltage burdenof the meter

should be zero in order for it to have no loading effect, If burden voltage is too high, its effects can degrade the source accuracy considerably.

/R) of

refer

To see how burden voltage can upset source accura to Figure 3-24. The passtve current source (AMPS the Model 263 is shown connected to the input of an electrometer or picoammeter. The burden voltage of the meter is represented by a constant voltage source at the input as V, If V0 were zero, the current seen by the meter

would simply be:

The instrument’s ability to measure the internal temperature (approximately once every second) makes temperature compensation possible. When the instrument is calibrated the resistor is measured while it is “cold” (just turned on; approximately 2PC). ‘lhis reading (Rx& at the

“cold” temperature (TaEF) is remembered by the instru-

ment. After the unit warms up, the resistor is measured (R) at the “hot” temperature (T). Because the instrument knows the change in resistance (AR) and the change in temperature (AT), it can calculate the actual TC of the resistor.

Sourcing Resistance - When sourcing resistance, the display will track the calculated output resistance. If temperature compensation is disabled by front panel Pro-

gram tc (see paragraph 3.9.3), the instrument will only

display the “hot” resistance value. This was the measured

value (when calibrated) of the resistor after the instrument was allowed to warm up.

Sourcing Current or Charge - When sourcing current or charge, voltage changes appropriately as the resistance changes in order to maintain the output at the rogr-ed current/charge setting. For example, on the or 2nC range the lGI7 resistor is used. If the resistor was measured to be l.OOlGII, the voltage source will be set

However, if V0 has a non-zero value, the current now becomes:

vs - vo

The accuracy specifications of AMPS V/R and COLIC V/R include the error contributed by meters that have a burden voltage of lOO$ or leas. When using meters that exceed a burden voltage of ICI&V, the additional sourcing error can be calculated as follows:

IV,/ - lav

Additional Error (in Amps) =

where Fs; The output resistance of the selected range (see labable

I = The amps or coulombs setting on the Model 263.

3-26

PASSIVE (V/R)

CURRENTSOURCE

OPERATION

r____--___-__~ I

MEIER

L -----__ -__-__

Figure 3-24. Burden Voltage Considerations

Table 3-5. Output Resistance of Passive Sources

Range

AMPS V/R / COUL V/R

Output Resistance (RJ

I I

2Oti

2mA

200 &A

20 fiA

ALA

200 nA

20 nA

2 nA

200 pA

20 pA

2p.4

2opc

200nC

20nC

2nC

zoopc

2opc

1 kfl 10 kR 10 kR

100 khl

1MQ

lOM0

1OOMQ

1GR 10GO

lOOGO 100GR

The additional error is added to the basic accuracy specification. The offset specification is not affected. If the burden voltage is less than lOO,V, the basic accuracy specification is not degraded.

NOTE

Adjusting the burden voltage of electrometers and

---__-__-____

picoammeters is part of their normal calibration routine. As the input voltage is adjusted to near zero, the burden voltage becomes near zero. Thus, at the time of meter calibration, burden voltage can be adjusted to be better than its specification.

3.11.3 Guarding Guarding uses a conductor at essentially the same poten-

tial seen at output high. The guard is supplied by a lowimpedance voltage source and is used to surround output high. Maintaining the guard conductor at the same potential as output high results in drastically reduced cable leakage currents.

Figure 3-25 shows the three conductors in a triax cable. Source low is normally connected to the inner shield of the cable. In this unguarded configuration, leakage current will flow through the insulator (represented by Q and C,) separating source Hl from source LO. Whether or not this leakage current causes a problem depends on the source and the load. For the following examples, assume Rr is lOOG% This is the rated insulator leakage resistance of the supplied triax cable.

3-27

OPERATION

OUTER SHIED OUTER SHIED

HI O- HI O-

TOSOURCE TOSOURCE

loo loo

Figure 3-25. Unguarded Triax Cable

Sourcing Resistance-This example will demonstrate how

cable insulator resistance affects a resistance source. The

source is set to output 1GQ to an electrometer. In the unguarded configuration, the source resistance (Ro) of 1Gn would be in parallel with the resistance of the insulator. The resulting resistance that would be measured

by the electrometer is calculated as follows:

o”T = - =

Q + R,

Rs x R,

1GQ x lOOGil 100Gfl

= - = 0.99GO

1Gll + 100GR 101GR

Instead of delivering 1GR to the electrometer, only 0.99GQ is measured at the output because of the leakage resistance. Leakage resistance contributes 1% error to the

measurement.

Sourcing Current - Leakage current in an unguarded circuit is a problem when sourcing current to a high impedance load. For example, assume the source is set to output 1nA to a 1GQ load. The 1GQ load will be in parallel with the leakage resistance (100GQ resulting with

z 990pA being delivered to the load. The other 10pA will leak through the insulator. The end result is a 1% sourcing error.

Figure 3-26 shows the general technique to guard the

source. Source low is rerouted to the outer shield of the

cable and a guard potential (V,) is connected to the inner shield. The guard voltage is at the same potential as source high and the guarded inner shield surrounds output high. Because the voltage potential at source high and source low is virtually the same, leakage current through the insulator will be almost zero. Generally, the guard and HI

differ by a small offset voltage (=SOpV). The resultant leakage current (Id would be:

5ojJv

I, = ~ = 500pA

lOOGO

Leakage current will flow from the inner shield to the outer shield (through RO), but it does not matter since the cm= rent is supplied by the guard source (V,) and not source high.

Whiie an advantage of guarding is a reduction of the ef-

fects of leakage resistance, a more important one is the reduction of the effective output capacitance (C,). The rise time of the source depends on the output resistance and the capacitance seen at the load. Thus, for high resistance

sourcing, even a small amount of cable capacitance can result in very long rise times. For example, a cable capacitance of of 1000pF and a resistance of 1OOGQ will result in a RC time constant of 100 seconds. guarding would drastically reduce cable capacitance resulting in

much faster rise times.

3-28

OPERATION

Figure 3-26. Guarded Triax Cable

3-2913-30

SECTION

IEEE-488 Programming

4.1 INTRODUCTION

The IEEE-488 bus is an instrumentation data bus with hardware and programming standards originally adopted by the IEEE (Institute of Electrical and Elearonic Engineers)

in 1975 and given the IEEE-488 designation. In 1978, stan-

dards were upgraded into the IEEE-488~1978 standards. The Model 263 conforms to these standards.

4.2 BUS CONNECTIONS

The following paragraphs provide the detailed informa-

tion needed to connect instrumentation to the IEEE-488 bus.

(A) SIMPLE SYSTEM

4.2.1 Typical Controlled Systems

System configurations are as varied as their applications. To obtain as much versatility as possible, the IEEE-488 bus was designed so that additional instrumentation could be

easily added. Because of this versatility, system complexity

can range from the very simple to extremely complex.

Figure 4-l shows two possible system configurations. Figure 4-1(A) shows the simplest possible controlled

system. The controller is used to send commands to the

instrument, which sends data back to the controller.

The system in Figure 4-1(B) is somewhat more complex in

coNrRcuER INSTRUMENT

(B) ADDITIONAL INSTRUMENTATION

Figure 4-1. System Types

MODEL 263

INSTRUMENT

4-l

IEEE-488 PROGRAMMING

that additional instruments are used. Depending on programming, all data

may

be routed through the controller,

or it may be sent directly from one instrument to another.

4.2.2 Cable Connections

The Model 263 is to be connected to the IEEE-488 bus

through a cable equipped with standard IEEE-488 connec-

tars, an example of which is shown in Figure 4-2. The connectar is designed to be stacked to allow a number of parallel connections. Two screws are located on each con-

nectar

standards call for metric threads, as identified by dark col-

ored screws. Earlier versions had different screws, which

are silver colored. Do not attempt to use these type of con-

nectars with the Model 263 which is designed for metric

to ensure that connections remain secure. Current

ne&d to the controller. Some controllers have an IEEE-488 type connector, while others do not. Consult the instruction manual for your controller for the proper connecting method.

NOTE

The IEEE-488 bus is limited to a maximum of 15

devices, including the controller. Also, the maximum cable length is limited to 20 meters, or 2 meters times the number of devices, which ever is less. Failure to heed these limits may result in erratic bus operation.

Custom cables may be constructed by using the informa-

tion in Table 4-l and Figure 4-5. Table 4-1 lists the contact

assignments for the various bus lines, whiie Figure 4-5 shows contact assignments.

CAUTION The voltage between IEEE-488 common and chassis ground must not exceed 30V or instrument damage may occur.

Table 4-l. IEEE-488 Contact Designation

Figure 4-2. IEEE-488 Connector

A typical connecting scheme for the bus is shown in Figure 4-3 Each cable normally has the standard connector on each end. These connectors are designed to be stacked to allow a number of parallel connections on one instrument.

NOTE

To avoid possible damage, it is recommended that you stack no more than three connectors on any

one instrument.

Connect the Model 263 to the cable as follows:

1. Line up the connector on the cable with the connector on the rear panel of the instrument. Figure 4-4 shows the IEEE-488 connector.

2. Tighten the screws securely, but do not overtighten them.

3. Add additional connectors from other instruments, as required.

4. Make sure the other end of the cable is properly con-

Number

contact

Designation

DIOl

D102

D103

D104

EOI (24)*

DAV

NRFD NDAC

IFC 10 11 12 13

SRO AT% SHIELD DI05 D106

D107

DI08

REN (24)* is’ 19 20 21 22 23

Gnd, (6)*

Gnd, (7)*

Gnd, (8)* Gnd. (9)* Gnd; (lb)* Gnd, (ll)* Gnd, LOGIC

in parenthesis reters to signal ground return ot

. .

IEEE-488 Type

Data Data

Management

Handshake Handshake Handshake Management Management Management

Ground Data Data Data Data Management

Ground

reference contact number. EOI and REN signal lines return on contact 24.

4-2

IEEE-488 PROGRAMMING

Figure 4-3. IEEE-488 Connections

30” MAX

Figure 4-4. Model 263 Rear Panel IEEE-488

Connector

Figure 4-5. Contact Assignments

4.3 PRIMARY ADDRESS PROGRAMMING

The Model 263 must receive a listen command before it will respond to addressed commands. Similarly, the unit must receive a talk command before it will transmit its

4-3

IEEE-488 PROGRAMMING

data. The Model 263 is shipped from the factory with a programmed primary address of 8. Until you become more familiar with your instrument, it is recommended that you leave the address at this value because the programming examples included in this manual assume that address.

The primary address may be set to any value between 0 and 30 as long as address conflicts with other instruments are avoided. Note that conrollers are also given a primary address, so you must be careful not to use that address either. Most frequently, controller addresses are set to 0 or 21, but you should consult the controller’s instruction manual for details. Whatever primary address you choose, you must make certain that it corresponds with the value specified as part of the controller’s programming language.

To check the present primary address or to change to a new one, perform the following procedure:

1. Press the MENU button until the current primary address is displayed. For example, if the instrument is set to primary address 8, the following message will be

displayed:

IEEE 8

2. To retain the current address, press MENU until the instrument exits the front panel program mode.

3. To change the primary address, do so using the ADJUST buttons and press MENU once to exit the program mode. The new address will be stored in memory so that the instrument will power up to that address.

4.4.1 Controller Handler Software

Before a specific controller can be used over the IEEE-488 bus, it must have IEEE-488 handler software installed. With some controllers, the software is located in ROM,

and no software initialization is required on the part of

the user. With other controllers, software must be loaded

from disk or tape and be properly initialized. With the

HP-85, an additional I/O ROM that handles interface func-

tions must be installed.

Other small computers that can be used as IEEE-488 con-

trollers may have limited capabilities. With some, inter-

face programmin

being used. Often little software “tricks” are required to

obtain the desired results.

From the preceding discussion, the message is clear: make

sure the proper software is being used with the interface.

Often, the user may incorrectly suspect that the hardware

is causing a problem when it was the software all along.

g functions may depend on the interface

4.4.2 Interface BASIC Programming Statements

The programmin g instructions covered in this section use examples written with Hewlett Packard Model 85 BASIC. This computer was chosen for these examples because of its versatility in controlling the IEEE-488 bus. This section covers those statements that are essential to Model 263 operation.

Note: Each device on the bus must have a unique primary address. Failure to observe this precaution will probably result in erratic bus operation.

4.4 CONTROLLER PROGRAMMING

There are anumber of IEEE-488 controllers available, each of which has its own programming language. Also, different instruments have differing capabilities. In this section, we will discuss the programming language for the HP 85 computer.

NOTE

Controller programming information for using the IBM-PC interfaced throueh a Caoital Eauioment Corporation (CEC) IEEE-488 inte&e is {o&ted in Appendix D. See Appendix E for other controller example programs.

4-4

A partial list of HP-85 BASIC statements is shown in Table 4-2. HE-85 BASIC statements have a one or three digit

argument that must be specified as part of the statement.

The first digit is the interface select code, which is set to

7 at the factory. The last two digits of those statements,

requiring a3digit argument, specify the primary address.

Those statements with a 3-digit argument listed in the

table show a primary address of 8 (the factory default primary address of the Model 263). For a different address, you would, of course, change the last two digits to the required value. For example, to send a GTL command to

a device using a primary address of 28, the follmving state-

ment would be used: LOCAL 728.

Some of the statements have two forms; the exact configuration depends on the command to be sent over the bus. For example, CLEAR 7 sends a DCL comman

CLEAR 708 sends the SDC command to a device with a

primary address of 8.

d, while

IEEE-488 PROGRAMMING

Table 4-2. BASIC Statements Necessary to Send

Bus Commands

Action Transmit string to device 08.

Obtain string from device 08. Send GTL to device 08. Send SDC to device 08. Send DCL to all devices. Send Remote Enable. Cancel Remote Enable. Serial poll device 08. Send Local Lockout. Send IFC

HP-65 Statement

4.5 FRONT PANEL ASPECTS OF IEEE-488 OPERATION

The Model 263 has a number of front panel messages associated with IEEE-488 programming. These messages, which are listed in Table 4-3, are intended to inform you of certain conditions that occur when sending devicedependent commands to the instrument. The following paragraphs describe the front panel error messages associated with IEEE-488 programming.

4.5.1 A bus error will occur if the instrument receives a device-

dependent command when it is not in remote, or if an illegal device-dependent command (IDDC) or illegal device-dependent cornman instrument. Under these conditions, the complete cornmand string will be rejected and the following message will be displayed:

In addition, the error bit in the serialpoll byte (paragraph

4.7.9) and pertinent bits in the Ul word will be set (paragraph 4.7.12). The instrument can be programmed to generate an SRQ under these conditions.

A no remote error can occur when a command is sent to the instrument when the REN line is false. Note that the

state of REN is only tested when the X character is re-

ceived. An IDDC error can occur when an invalid command such as ElX is transmitted (this command is invalid because the instrument has no command associated with that letter). Similarly, an IDDCO error occurs when an irvalid option is sent with a valid command. For example, the command F9X has an invalid command because the instrument has no such command option.

Bus

Errors

d option (IDDCO) is sent to the

bErr

Another front panel aspect of bus operation is local lockout (LLO). Front panel controls are functional unless the LLO command was asserted. See paragraph 4.6.3 for more in-

formation on LLO.

Table 4-3. IEEE-488 Front Panel Messages

bErr

nElT

I’

out

star

Bus error, no remote, IDDC or IDDCO. Number error. Invalid value command

(A, L or V).

Flashing exponent decimal point(s) indi-

cate that calibration constants were changed but not stored (temporary calibration). Also flags an NVRAM error on power up. Calibration switch in disable position.

Permanent storage of calibration constant

(in NVRAM) not performed. Permanent storage (in NVRAM) of cal constants performed. Calibration switch in enable position.

HP-85 Programming Example-To demonstrate a bus error, send an IDDC with the following statements:

OUTPUT 708;“ElX”

When the statement is executed, the bus error message appears on the display for about one second.

4.5.2 Number Errors A front panel error message is used to flag a number er-

ror. A number error occurs when an out of range calibration value (A or L) or output value (V) is sent over the bus. A number error also occurs if the V command is sent while in the OHMS function. A number error will cause the value command to be ignored. However, other commands in the command sequence will be executed. The following message is displayed briefly when a number error occurs:

nEl.r

The instrument can be programmed to generate an SRQ

4-5

IEEE-488 PROGRAMMING

when a number error occurs (see paragraph 4.7.9).

HP-85 Programming Example--To demonstrate a number error, enter the following statements into the computer:

OUTPUT 708;“VlOOX”

When END LINE is pressed, a number error will occur because an output value of 100 cannot be programmed.

4.5.3 Calibration Storage Messages

‘here are three messages associated with storage of

rlibration constants.

The calibration switch must be in the ENABLED position to permanently store (in NVRAM) calibration constants.

If the switch is in the DISABLE position, calibration will

be temporary and will be lost when the instrument is

turned off.

Storage of each calibration constant occurs automatically when a call%ration value command (A or L) is sent over the bus. If a calibration value is sent with the calibration switch in the ENABLE position, the following message will be displayed briefly to indicate permanent storage:

Stor

If a calibration value is sent with the calibration switch in the DISABLE position, the following message will be displayed briefly to indicate temporary storage:

out

In addition, the exponent decimal point(s) will blink on and off to indicate that the calibration value is temporary. One exponent decimal point (i.e. “V.“) blinking indicates that the L command was sent and both exponent decimal points (i.e. “.V.“) indicate that the A command was sent.

NOTE

Blinking exponent decimal point(s) are also used to indicate an NVRAM failure. NVRAM is tested on power up and when the device is cleared (DCL or SDC). In the event of a failure, refer to the troubleshooting information in Section 8 of this manual.

4.6 GENERAL BUS COMMANDS

General bus commands are those commands such as DCL that have the same general meaning regardless of the instrument type. Commands supported by the Model 263 are listed in Table 4-4 which also lists BASIC statements necessary to send each command. Note that commands requiring that a primary address be specified assume that the Model 263 primary address is set to 8 (its default address).

4.6.1 REN (Remote Enable)

The remote enable command is sent to the Model 263 by

the controller to set up the instrument for remote operation. Generally, the instrument should be placed in the remote mode before you attempt to program it over the

bus. Simply setting REN true will not actually place the

instrument in the remote mode. Instead the instrument must be addressed after setting REN true before it will go into remote.

4-6

Table 4-4. General Bus Commands and Associated BASIC Statements

HP-85

Command Statement

REN

IFC

GTL

DCL

SDC

Affect On Model 263

Goes into remote when next addressed

Goes into talker and listener idle states

Front panel controls locked out

Cancel remote Returns to default conditions Returns to default conditions

Cancel LLO

IEEE-488 PROGRAMMING

To place the Model 263 in the remote mode, the controller must perform the following sequence:

1. Set the REN line true.

2. Address the instrument to listen.

HP-85 Progmnming Example-This sequence is automatically performed by computer when the following is typed into the keyboard.

After the END LINE key is pressed, the instmment will be in the remote mode, as indicated by the REMOTE light. If not, check to see that the instrument is set to the proper primary address 8, and check to see that the bus connections are properly made.

4.6.2 IFC (interface Clear)

The IFC command is sent by the controller to place the Model 263 in the local, talker and listener idle states. The unit will respond to the IFC command by cancelling front

panel TALK or LISTEN lights, if the instrument was previously placed in one of those modes.

REN must be true for the instrument to respond to LLO. REN must be set false to cancel LLO.

To send the LLO command, the controller must perform the following steps:

1. Set ATN true.

2. Place ‘the LLO command on the data bus.

HP-85 Programming Example-The LLO

cornman d is sent

by entering the following statement:

After the END LINE key is pressed, the instrument’s front panel controls will be locked out.

4.6.4 GTL (Go To Local) and Local

The GTL command is used to take the instrument out of the remote mode. With some instruments, GTL may also cancel LLO. With the Model 263 however, REN must first be placed false before LLO will be cancelled.

To send the IFC command, the controller need only set

the IFC line true for a miniium of 100rsec.

HP-85 Progr

amming Example-Before demonstrating the IFC command, turn on the TALK indicator with the following statements:

At this point, the REMOTE and TALK lights should be on. The IFC command can be sent by entering the following statement into the computer:

KFClRTIO 7

After the END LINE key is pressed, the REMOTE and TALK lights will turn off, indicating that the instrument has gone into the talker idle state.

4.6.3 LLO (Local Lockout)

To send GTL, the controller must perform the following

sequence:

1. Set ATN true.

2. Address the instrument to listen.

3. Place the GTL command on the bus.

HP-85 Programming Example-Place the instrument in the remote mode with the following statement:

F:EP,,jTE 7,X

Now send GTL with the foIlowing statement:

Ll:lcciL 7Elc:

When the END LINE key is pressed, the front panel REMOTE indicator goes off, and the instrument goes into the local mode. To cancel LLO, send the following:

LrJCAL 7

The LLO command is used to remove the instrument from the local operating mode. After the unit receives LLO, al! its front panel controls except POWER will be inoperative,

4.6.6 DCL (Device Clear)

The DCL command may be used to clear the Model 263

4-7

IEEE-488 PROGRAMMING

and return it to its power-up default conditions. Note that the DCL command is not an addressed command, so all instruments equipped to implement DCL will do so simultaneously. When the Model 263 receives a DCL command, it will return to the power-up default conditions.

To send the DCL command, the controller must perform the following steps:

1. Set ATN true.

2. Place the DCL command byte on the data bus.

HP-85 Programming Example-Place the unit in an operating mode that is not a power-up default condition. Now enter the following statement into the computer keyboard:

CLEAF: ;

When the END LINE key is pressed, the instrument returns to the power-up default conditions.

4.6.6 SDC (Selective Device Clear)

The SDC command is an addressed command that performs essentially the same function as the DCL command. However, since each device must be individually ad-

dressed, the SDC command provides a method to clear only a single, selected instrument instead of clearing all instruments simultaneously, as is the case with DCL. When the Model 263 receives the SDC command, it will return to the power-up default conditions.

To transmit the SDC command, the controller must perform the following steps:

1. Set ATN true.

2. Address the Model 263 to listen.

3. Place the SDC command on the data bus.

After END LINE is pressed, the instrument returns to the power-up default conditions.

4.6.7 SPE, SPD (Serial Polling)

The serial polling sequence is used to obtain the Model 263 serial poll byte. The serial poll byte contains irnportant information about internal functions, as described in paragraph 4.7.9. Generally, the serial polling sequence is used by the controller to determine which of several instruments has requested service with the SRQ line. However, the serial polIiig sequence may be performed at any time to obtain the status byte from the Model 263.

The serial polling sequence is conducted as follows:

1. The controller sets ATN true.

2. The controller then places the SPE (Serial Poll Enable) command byte on the data bus. At this point, all active devices are in the serial poll mode and waiting to be addressed.

3. The Model 263 is then addressed to talk.

4. The controller sets ATN false.

5. The instrument then places its serial poll byte on the data bus, at which point it is read by the controller.

6. The controller then sets ATN true and places the SPD (Serial Poll Disable) command byte on the data bus to

end the serial polling sequence.

Once instruments are in the serial poll mode, steps 3 throu talk i the address is transmitted and false when the status byte is read.

HP-85 Programming Example-The SPOLL statement automatically performs the sequence just described. To

demonstrate serial polling, enter in the following statements into the computer:

h 5 above can be repeated by sending the correct

a dress for each instrument. ATN must be true when

HP-85 Programming Example-Place the unit in an operating mode that is not a power-up default condition. Now enter the following statement into the computer keyboard:

4-8

When the END LINE key is pressed the first time, the computer initiates the serial polling sequence. The decimal value of the serial poll byte is then displayed on the computer CRT when END LINE is pressed the second time.

IEEE-488 PROGRAMMING

4.7

DEVICE-DEPENDENT COMMANDS

This section contains the information needed to control the Model 263 over the IEEE-488 bus using the device-dependent commands. A programming example using the HP-85 computer is included for each device-dependent command.

Note: It is assumed that the user is already familiar with kont panel operation

4.7.1

IEEE-488 device-dependent commands (summarized in Table 4-5) are used with the Model 263 to control various operating modes such as function, range and guard. Each command is made up of a single

ASCII letter followed by a number representing a command option. For example, a command to control the measuring function is programmed by sending an ASCII “F” followed by a number representing the function option. The IFEE- bus actually treats these commands as data in that ATN is fake when the commands are transmitted.

A number of commands may be grouped together in one string. A command string is usually terminated with an ASCII “X” character, which tells the instrument to execute the command string. Commands sent without the execute character will not be executed at that time, but they will be retained within an internal command buffer for execution at the time the X character is received. If any errors occur, the instrument will display appropriate front panel error messages and generate an SRQ if progmrnrned to do so.

Device-dependent commands affect the Model 263 much like the front panel controls. Note that commands are not necessarily executed in the order received. Thus to force a particular command sequence, you would follow each command with the execute character (X), as in the example string, ZlXFOX, which will zero the output and then select the ohms function. The order of presentation in Table 4-5 is the actual order that DDCs are executed. Note that the X command is listed first since it is the character that forces the execution of the rest of the commands.

Device-dependent commands can be sent either one at a time, or in groups of several commands within

a single string. If a particular command occurs n times in a command string, then the “nth” occurrence is the only one used, e.g., F2F4FOX goes to FOX only. Some examples of valid command strings include:

Programming Overview

FOX - Single command sting.

FOKlR2X - Multiple command string.

F6 X Spaces are ignored.

Typical invalid command strings include:

ElX Invalid command, as E is not one of the instrument commands.

F9X - Invalid command option because 9 is not an option of the F command

If an illegal command (IDDC) or illegal command option (IDDCO), is sent, or if a command string

is sent with REN false, the string will be ignored.

4-9

IEEE-488 PROGRAMMING

Device-dependent commands that control the Model 263 are listed in Table 4-5. These commands are covered in detail in the following paragraphs. The associated programming examples show how to send the commands with the HP-85.

NOTE Programming examples assume that the Model 263 is at its factory default value of 8. In order to send a device-dependent command, the controller must perform the following steps:

1. Set ATN true.

2. Address the Model 263 to listen.

3. Set ATN false.

4. Send the command string over the bus one byte at a time.

NOTE REN must be true when sending device-dependent commands to the instrument, or it will ignore the command and display a bus error message.

General HP-85 Programming Example-Device-dependent commands may be sent from the HP-85 with the following program:

When this short program is run, it will prompt you to enter a command string (line 10). If, for example, the command string F2X is entered, the instrument will go to the volts function (line 20) after END LINE is pressed. The program will then prompt for another command string.

Table 4-5. Device-Dependent Command Summary

Mode Execute Function

1 Corn :mand Description

X Execute other device-dependent commands

FO OhIllS

Amps volts

Coulombs F4 F5 External Volts

F6 Ladder F7

V/R Amps

V/R Coulombs

Paragraph

4.7.15

4.7.4

4-10

IEEE-488 PROGRAMMING

Table 4-5. Device-Dependent Command Summary (Cont.)

Auto On Auto

4-11

4.7.2

A (Calibration)

Purpose Format Parameters Description

Use to send calibration values over the bus.

An.nnnnnE*nn Calibration value using exponent. In general, calibration of the Model 263 over the IEEE-488 bus consists of sourcing

a signal to an electrometer and sending the correspondmg calibration value over the bus. There are actually two calibration commands used to calibrate the Model 263; the A comman d and the L command. The A command is used for all but “cold” calibration of the lGQ, lOGa and 1OOGQ resistors. The L command (see paragraph

4.7.8) is used to “cold” calibrate these ranges.

When calibrating VOLTS, the least significant digit (LSD) of the Model 263 display can only be zero or five. For this reason the Model 263 will round a 5% digit A calibration command value for volts, as follows:

1. If the LSD of the command value is 1 or 2, the LSD on the display will be rounded to 0. Example: Sending A1.90252X will result in a display reading of 1.90250.

2. If the LSD of the command value is 3, 4, 6 or 7, the LSD on the display will be rounded to 5. Example: Sending A1.902.54X will result in a display reading of

1.90255.

3. If the LSD of the command value is 8 or 9, the display will round to 10. That is, the LSD will be 0 and the next more significant digit will increment (carry) by one unit. Example: Sending Al.90258 will result in a reading of 1.90260.

Note: A value cannot increment past full scale of the range it is currently on. In-

stead, the value will limit at 199995 counts.

~o~~~IIllTliIlg 1. Only as many significant digits as necessary need be sent. Examples:

Send A1.9E-9X instead of A1.9000E-09X Send A1.9X instead of A1.9000X

2. The instrument will ignore the digits of any calibration command value that ex-

ceeds 5% digits. For example, if a value of 1.902587 is sent, the seven will be ignored and 1.90260 will be displayed.

PrOgrafllmiIlg

Examples

CAUTION: The following examples are only intended to show send calibration co tent sending of the A command may adversely affect calibration of the Model 263. A complete IEEEr488 calibration program is contained in Section 8 (Maintenance)

of this manual.

UIJTPCIT 7W; 6

CllJTPlJT 708, i d AZ+’ 3

mounds when actually calibrating the instrument. The inadver-

~Ai9.3E-12X~ ? ! Send cal value of 19.9 x lo-l1

! Send cal value of 2.

proper syntax.

Only

4-12

4.7.3 C (Temperature Compensation)

IEEE-488 PROGRAMMING

Purpose Format

Parameters

Default

Description

Disable and enable the temperature compensation feature of the instrument.

CO Temperature compensation disabled Cl Temperature compensation enabled

Upon power up, or after a DCL or SDC command is received, temperature compensation will enable (Cl).

The instruments ability to measure the internal operating temperature, makes it possible for it to track the actual resistance of the lGQ, lOG0 and 1OOGn resistor. When the instrument is calibrated, the actual temperature coefficient of each resistor is established. The instrument can then calculate the value of each of those resistors at any temperature (see paragraph 3.11.1).

Sending CO disables temperature compensation. With temperature compensation disabled, the instrument uses the resistor reading that was measured (during “hot” calibration) when the internal temperature approximated the normal operating temperature.

Sending Cl enables temperature compensation. With temperature compensation enabled, the instrument constantly monitors temperature and calculates the resistance of the lG0, 1OGQ and 1OOJ.X resistors.

Programming Examples

If displaying the status of temperature compensation (Program tc), the display will not immediately update when the alternate C command is sent. Press the MENU button to scroll back around to Program tc to update the temperature compensation status message.

,:,,JTP,JT 70;‘:.; 6 6 i;ij::c:~ 5 ,I,,JTPlJT 7#:3i i 6 ,Cl:::f ’

! Disable temperature compensation ! Enable temperature compensation

4-13

4.7.4

F (Function)

Purpose

Format

Parameters

Description

Use to select the operating mode of the instrument.

FO Ohms Fl Amps F2 Volts F3 Coul F4 Amps V/R F5 EXT INPUT F6 Ladder F7 Coul V/R

The four basic functions of the Model 263 are ohms (FO), amps, volts, and coulombs. The Fl and F3 functions use the active current source. The output accuracy of this source is not affected by burden voltage or loading, as long as compliance voltage is not surpassed. The F4 and F7 functions use the passive (V/R) current source. This current source has less offset, and is intended primarily for devices that have a very low input voltage burden. The internal voltage source (F2) is used to source up to

f 19.9995V. An external source (up to 200V peak, lOOmA peak) can applied to EXT INPUT on the rear panel of the Model 263. The F5 command is used to connect the external source to the output of the Model 263.

The calibration “ladder” (F6) is used to calibrate the high ohms ranges (1OMQ -

lOOG62) of the Model 263. This calibration method uses PREAMP DUT voltage

readings of the Model 263 as calibration values instead of the actual resistance

measurements of the resistors. This method eliminates the need for precision equipment that would be needed to accurately measure the high ohm resistors. By using the “ladder”, a single precision DMM (such as the Keithley Model 196 DMM) can

be used to calibrate the Model 263.

Default

~o;~t’atIIIIIitIg Whenever an F command is sent, the instrument goes into standby,

PrOgramIllirlg OIJTPUT

Upon power-up or after the instrument receives a DCL or SDC, the VOLTS function will be selected.

70%; i i

Fix’

! Select AMPS function.

Example

4-14

IEEE-488 PROGRAMMING

4.7.5

G (Prefix)

Purpose Format Parameters

Default

Description

Controls the format of the output string sent by the instrument.

GO Send prefix with reading Gl Do not send prefix with reading

Upon power up, or after a DCL or SDC command is received, the instrument will transmit readings with the prefix (GO).

The prefix identifies the reading that is sent over the bus. Figure 4.6 shows the format for these readings.

Program for no prefix Send reading to computer Display no prefix reading on CRT Program for prefix Send reading to computer Display reading with prefix

PREFIX 7

MANTISSA (5 1/2 DIGITS)

N = NORMAL S = STANDBY 0 = OVER COMPLIANCE

(AMPS AND COUL)

Figure 4-6. General Data Format

- IW

* 1.

90000

OHM =OHMS

DCA = AMPS DCV = VOLTS DCC = COULOMBS VRA = V/R AMPS DCX = EXTERNAL VOLTS LDR = LADDER VRC = V/R COULOMBS

E-12

EXPONENT

4-15

IEEE-488 PROGRAMMING

4.7.6 Purpose

Format

PSGNnStSrS JO Perform self-tests

Description

Programming

(Self-test)

Use J command to perform tests on its read-only memory (ROM).

Self-Test--When the JO command is sent over the bus, the instrument performs the ROM test. If the self-test is successful, the self-test error bit in the Ul status word will be set to 0. Otherwise, a failure will set this bit to 1.

ClClTPLlT

708.; i L ,ir3:iv 5 ! Perform self-tests

Note

416

IEEE-488 PROGRAMMING

4.7.7

K (EOI)

Purpose Format Parameters

Default

Description

PrOgraIlllllitlg

Notes

Enable/disable EOI.

KO EOI enabled Kl EOI disabled

Upon power-up, or after the instrument receives a DCL or SDC command, the in-

strument will return to the KO mode.

The EOI line provides one method to positively identify the last byte in the data

string sent by the instrument. When enabled, EOI will be asserted with the last byte

the instrument sends over the bus.

1. Some controllers rely on EOI to terminate their input sequences. Suppressing EOI may cause the controller input sequence to hang.

2. When enabled, EOI will be asserted with the last byte in the terminator (if enabled), or with the last byte in the data string if the terminator has been disabled.

4-17

IEEE-488 PROGRAMMING

4.7.6

L (Calibration; Low Temperature Point)

Purpose

Format Parameters Description

Programming Notes

Programming Example

Use to send calibration values to calibrate the low (“cold”) temperature point for the lG& lOG0 and 1OOGn resistors.

Ln.nnnnEnn Calibration value using exponent.

In general, each of the three gigaohm resistors are calibrated at two temperature points so that temperature coefficient (TC) profiles can be established. Because the instrument constantly measures its internal temperature and knows the actual TC of each gigaohm resistor, it can calculate the actual resistance of the resistor at any temperature. This is the temperature compensation feature of the instrument. The L command is used to send the calibration value for each of the three gigaohm resistors at the low (“cold”) temperature point. The A calibration command is used

to calibrate the high (“hot”) temperature point of the gigohm resistors (see paragraph

4.72).

1. Only as many significant digits as necessary need be sent. Example: Send Ll.OlE9X instead of Ll.OllNE09X

2. The instrument will ignore the digits of any calibration value that exceeds 5% digits. For example, if a calibration command value of 1.882067 is sent, the seven will be ignored and 1.88206 will be displayed.

CAUTION: The following example is only intended to show proper syntax. Only

send calibration commands when actually calibrating the instrument. The inadvertent sending of the L command may adversely affect calibration of the Model 263. A complete IEEE-488 calibration program is contained in Section 8 (Maintenance)

of this manual.

,:,,JTp,jT 78:3 ,: 6 6 F<,F:4L1 :3:32’r3F,E’3>.:! ?

! Calibrate low temperature point of 1Gfl

resistor using the “ladder”.

418

IEEE-488 PROGRAMMING

4.7.9 M (SRQ Mask and Serial Poll Byte Format)

Purpose Format

Parameters

Default

Description

Program which conditions will generate an SRQ (service request).

MO SRQ disabled M2 Charge done Ml6 Ready M32 Error

Upon power up, or after the instrument receives a DCL or SDC command, SRQ is disabled (MO).

SRQ Mask--The Model 263 uses an internal mask to determine which conditions will cause an SRQ to be generated. Figure 4-7 shows the general format of this mask, which is made up of eight bits. The Model 263 can be programmed to generate an SRQ under one or more of the following conditions:

1. When a charge is done (M2).

2. When the instrument is ready to accept bus commands (M16).

3. When an error condition occurs (M32).

Serial Poll Byte Format--The serial poll byte contains information relating to data

and error conditions within the instrument. The general format of the status byte

(which is obtained by using the serial polling sequence, as described in paragraph

4.6.7) is shown in Figure 4-7. Note that the various bits correspond to the bits in the SRQ mask as described above.

The bits in the serial poll byte have the following meanings: Bit 0 Not used; always set to zero.

Bit 1 (Charge Done) - Set when not sourcing charge. Cleared (0) while sourcing charge.

Bit 2 Not used; always set to zero. Bit 3 Not used; always set to zero.

Bit 4 (Ready) Set when the instrument has processed all previously received commands and is ready to accept additional commands over the bus. Cleared upon receipt of “X’.

Bit 5 (Error) - Set when one of the following errors have occurred:

1. An illegal device-dependent command (IDDC) or an illegal device-dependent command option (IDDCO) was transmitted.

2. The instrument was programmed when not in remote.

3. A number error has occurred.

4. A self-test error has occurred. This bit is cleared when the Ul status word is read to determine the type of error

(see paragraph 4.7.12). Bit 6 - Set if the Model 263 asserted SRQ. Cleared when the instrument is serial

polled. Bit 7 Not Used; always set to zero.

4-19

IEEE-488 PROGRAMMING

1 = SRQ BY 263

(SERIAL POLL BYTE 0

1= CHARGE WNE

Figure 4-7. SRQ Mask and Serial Poll Byte Format

Programming

. .

Notes

SRQ Mask:

1. The instrument may be programmed to generate an SRQ for more than one set of conditions simultaneously. To do so, simply add up the decimal bit values for the required SRQ conditions. For example, to enable SRQ under charge done

(MZ) and error (M32) send MNX.

2. To disable SRQ, send MOX. This command will clear all bits in the SRQ mask.

Serial Poll Byte:

3. If an error occurs, bit 5 (error) in the serial poll byte will latch and remain so until the Ul word is read (paragraph 4.7.12). The Ul status word will define the nature of the error.

4. The serial poll byte should be read to clear the SRQ line once the instrument has generated an SRQ. All bits in the serial poll byte will be latched when the SRQ

is generated. Bit 6 (SRQ) will be cleared when the serial poll byte is read.

5. Even with SRQ disabled, the serial poll byte can b@ read to determine appropriate instrument conditions. All set bits will remain latched until MO is asserted, power is cycled, or a DCL or SDC is sent. However, bit 5 can be cleared by reading the

Ul error status word.

! Program for SRQ on error. ! Attempt to program illegal com-

mand (IDDC). ! Serial poll the 263. ! Wait for SRQ to occur. ! Label the bit positions.

4-20

! Loop eight times. ! Display the bit positions

IEEE-488 PROGRAMMING

4.7.10

0 (Operate)

Purpose Format

Parameters

Default

Description

PrOgraIIIITIiIIg

Note Programming

Examples

Place the instrument in operate or standby.

00 Standby 01 operate

Upon power up, or after a DCL or SDC command is received, the instrument will go to standby (00).

In operate (Ol), the programmed source is available at the output of the Model 263.

In standby (00), the programmed source is removed from the output. On all functions, except coulombs, the lCOG0 resistor is placed on the output. For the coulombs function, zero coulombs, on the selected range, is placed on the output.

Anytime a function (F) command is received, the instrument will go to standby.

IllcITPcIT 7%:; i cO1::?s s

,I,lJTPlJT 701?; i i 100::~: * ?

! Place

! Place instrument in standby

instrument in operate.

4-21

IEEE-488 PROGRAMMING

4.7.11

Purpose

R (Range)

Controls the sensitivity (ranges) of the source functions,

Format Rn Parameters

R-l E

R4 1M

R5 10M 20 R6 1OOM

R9 1OOG 200 PA 20 R10 Rll 1OOG 2omA 20 R12 Auto Off Auto Off Auto Off Auto Off Auto Off

Upon power up, or after receiving a DCL or SDC command, the instrument will go to the 2oOn-W range (Rl).

Description

The range command gives the user control over the sensitivity of the instrument. The Fl through Fll commands perform essentially the same functions as the front panel RANGE buttons.

Ohms Amps Volts Coulombs Ladder

Auto On Auto On

100k 200 pA 20

(Fl, F4)

2pA

20 pA 2v 2oopc 1OML

2nA

IL4

200 nA 20

10G

100G

2~4

2mA

P-4

02)

Auto On Auto On Auto On

2oomv

v v

(F3, F7)

2opc

2nC

20nC 1GL

200nC 1OGL

2ojL

2cQLc 2oofic 1OOGL 2oopc 1OOGL

2oofic 1OOGL

0%)

1ML

1OOML

1OOGL 1OOGL 1OOGL

Programming Notes

Programming Examples

An added feature available over the bus is autorange for the volts, amps and coulombs functions. When FO is sent over the bus, autorange is selected. The range that the instrument goes to depends on the programmed value that is sent with a value command (V). The instrument will go to the lowest range (for best resolution) that can accomodate the value sent over the bus. Sending F12 over the bus disables autorange without affecting the present range.

1. The instrument can be placed in autorange (RO) while on the ohms function. However, since value commands are not recognized by the ohms function, RO has no affect on ohms range selection.

2. Sending Rl through Rll also disables autorange and places the instrument on

the range that corresponds to that command option.

OIJTPIJT 708; I’i FlR4X” ’ UUTPIJT 7138, ‘ L F2F:3X9 s

U,UTP,JT 708j 6 ‘F2R@1114:’ (

! Select 21~4 range.

! Select 2ov range. ! Select autorange; 263 will go to 2V range.

4-22

4.7.12 u (Status)

IEEE-488 PROGRAMMING

Purpose Format

Parameters

Default

Description

Access information concerning various operating conditions of the Model 263.

UO send machine status Word Ul send error status word U2 send data status word

Upon power up, or after a DCL or SDC is received, the machine status word (UO) will default to the values shown in Figure 4-8 and the bits in the error status word

(Ul) will clear (0).

When a U command is transmitted, the instrument will transmit the appropriate

status word instead of its normal data string when it is addressed to talk. The status

word will be transmitted only once for each U command. UO: The format of UO status is shown in Figure 4-8. The letters correspond to modes

programmed by the respective device-dependent commands. Returned values

correspond to the programmed numeric values. The values shown in the UO status word are the default values.

Ul: The Ul command allows access to Model 263 error conditions. The error status

word (Figure 4-9) is actually a string of ASCII characters representing binary

bit positions. Reading the Ul status clears the error bits. An error condition is

also flagged in the serial poll byte, and the instrument can be programmed to generate an SRQ when an error condition occurs (see paragraph 4.7.9).

The various bits in the Ul Error Status words are described as follows: IDDC--Set when an illegal device-dependent command (IDDC) such as ElX is

received (“E” is illegal). IDDCO--Set when an illegal device-dependent command option (IDDCO) such

as F9X is received (“9” is illegal). No Remote--Set when a progr Number--Set when a number error occurs. A number error occurs when an in-

valid value (V, A or L) command is received. Also, send a V command while in OHMS will result in a number error.

Self-Test--Set when the self-test has failed.

amming command is received when REN is false.

4-23

IEEE-488 PROGRAMMING

MODEL NUMBER (263) TEMPERATURE COMPENSATION (Cl

0 = Ternperanrre colnpensation off

FUNCTION (Fl

1 = Temperature compensation on

0 = Ohms 1 = Amps

2 = Volts 3 = Cd

4 = V/R Amps 5 = Ext Volts

6 = Ladder 7 = V/R Coul

RANGE (R) RllUXl m (Autorange) 0 = Autorange

off

GUARD 0 0 = Guard off

1 = Guard on PREFIX (G)

0 = Prefix 1 = No prefiv

OPERATE (0) 0 = Standby 1 = Operate

1 = Autorange on SRQ MASK OM) nn (Range)

Ohms Amps

01 = 1 kO

02 = 10 kR 03 = 100 kR

04 = 05 = 1OMi-l 06 =

lOOM0

200 pA 20 v

IMR

200 n4 20 v

20 pA 2 v

20 n.4 20 V

07 = 1Gi-l 2@ OS = lOGil

09 = 1OOGR 10 = lOOGO 2,n.b. 20 V 2OOpC 1OOGL

11 = lOOGO

200 pA 20

2OmA 20 V

VORS Gaul Ladder

2 PA 2oomv

2 n.4 20 v

20 V 20,tC 1OOGL 20 V 2OOpC 1OOGL

2opc

2oopc

20nC IGL

2nC

IML IOML

1OOML

200nC 10GL

2,tC 1OOGL

200&C

1OOGL

2OO,,C 100GL

ZERO (Z)

00 = Mask cleared

= Charge done

= Ready

32 = Error

EOI (K, 0 = EOI 1 = NoEOI

TERMINATOR ci) 0 = CR LF 1 = LF CR 2 = CR 3

= LF

4 = None

0 = zero off 1 = Zero on

4-24

Figure 4-9. UO Machine Status Word (Default Conditions Shown)

MODEL NO.

263

IDDC

l/O

IDDCO

1/o

NO REMOTE NUMBER SELF-TEST

l/O

110 l/O

OOOO<TERM>

Figure 4-9. Ul Error Status Word

U2: The U2X sequence allows access to instrument data conditions. The U2 word

is made up of ASCII characters representing binary values (0 or 1). The bits in the U2 status word are shown in Figure 4-10, and described as follows:

Uncalibrated. There are two situations that will cause this bit to set.

1. This bit will be set if a calibration value is sent with the calibration switch in the disable position.

IEEE-488 PROGRAMMING

2. This bit will be set if there was an NVRAM error on power up, or when DCL or SDC was sent over the bus. Calibration constants are stored in NVRAM.

Compliance Overload. Set when the voltage limit (approximately * 12V) of the current source has been reached.

Calibration Switch Enabled. Set when the calibration switch is in the enable positon.

MODEL NO.

263

PrOgrZItIIIning 1. The instrument

Notes

corresponding U command is transmitted.

2. The bits in the Ul word will latch (1) and remain that way until the Ul word is read.

The programmed terminator (default CR LFJ will be transmitted at the end of each

status word.

4. EOI will be transmitted at the end of the status word unless disabled with the

K command.

5. To make sure that correct status is transmitted, the status word should be requested as soon as possible after the command is transmitted.

6. The complete command string will be ignored if an IDDC, IDDCO or no remote error occurs. The message “bErr” is displayed when a bus error occurs.

7. Within the command string, only the command(s) causing a number error will be ignored. The message “nErr” is displayed when a number error occurs.

UNCALIBRATED

Oil

COMPLIANCE CALIBRATION

OVERLOAD

Oil O/l

SWlTCH ENABLED

000000<TERM>

Figure 4-10. U2 Data Status Word

will

transmit the appropriate status word only once each time the

! Dimension input string. ! Send UO command. ! Obtain UO status from 263. ! Display UO status word. ! Send Ul command. ! Obtain Ul status from 263. ! Display Ul status word. ! Send U2 command. ! Obtain U2 status from 263. ! Display U2 status word.

4-25

4.7.13

V (Output Value)

Purpose Format Parameters Description

Use to program the instrument to the desired output reading.

V *n.nnnnE inn Output value using exponent

The V command is used to program the output of the volts, amps and coulombs

sources. Valid values for the V command depend on the range that the instrument is on. For example, sending V3X with the instrument on the 2V range is invalid and will result in a number (“nErr”) error. However, if the the instrument is in autorange (RO), any value within the output range of the function will be valid. The instrument will go to the lowest possible range that can accommodate the value sent over the bus.

The least significant digit (LSD) of the Model 263 display can only be a zero or a five. For this reason the Model 263 will round a 5% digit V command value as follows:

1. If the LSD of the command value is a 1012, the LSD on the display will be rounded to a 0. Example: Sending V1.00252X will result in a display reading of 1.00250.

If the LSD of the command value is a 3, 4, 6 or 7, the LSD on the display will be rounded to a 5. Example: Sending V1.00254X will result in a display reading of 1.00255.

3. If the LSD of the command value is an 8 or 9, the display will round to 10. That is, the LSD will be 0 and the next more significant di it will increment (carry) by one unit. Example: Sending V1.00258 will result in a &play reading of 1.00260.

4. If a 199998 or 199999 count command value is sent, the instrument will display a 199995 count reading. The instrument cannot round up and carry because 199995 is the maximum reading that the Model 263 can display. For example, sending V1.99999X will result in a display reading of 1.99995. However, if the instrument

is in autorange (RO), it will instead uprange (if not already at the highest range)

and display a 20000 count reading. For example, sending ROV1.99999X, will cause the Model 263 to uprange and display a reading of 2.0000. On the highest range, the reading will limit at 199995 counts.

PrOgratIIIning

Notes

4.26

1. Only as many significant digits as necessary need be sent. Examples: Send V1.9E-9X instead of V1.9000E-09X

Send VlX instead of Vl.OOOOX

2. The instrument will ignore the digits of any command value that exceeds 5% digits. For example, if a value of 1.222228 is sent, the eighth will be ignored and 1.22220 will be displayed.

3. The V command will not work in the ohms function. If the V command is sent, the instrument will ignore the V command, generate a number (“nErr”) error, but execute any other commands sent in the same command sequence.

IEEE-488 PROGRAMMING

4.7.14 Purpose

W (Guard)

Use to enable or disable guard

Format Wn Parameters

Default

Description

Wl Enable guard Upon power up, or after a DCL or SDC command is received, guard will disable

W). When guard is enabled (Wl) the output of the Model 263 is reconfigured so that

a guard drive can be placed on the inner shell of the output triax connector. Depending on the function, the guard voltage may be supplied by the Model 263 or by an external drive. See paragraph 3.7 for detailed information on guard. When guard is disabled (WO) the output is placed back in the unguarded configuration.

Disable guard

4-27

4.7.15 X (Execute)

Purpose

Format Description

Programming Notes

Programming

Examples

Directs the Model 263 to execute device-dependent commands received since

previous “x”.

The execute command is implemented by sending an ASCII “X” over the bus. Its purpose is to direct the Model 263 to execute other device-dependent commands such as F (function) or R (range). Usually, the execute character is the last byte in the command string (a number of commands may be grouped together into one string); however, there may be certain circumstances where it is desirable to send

a command string at one time and then send the execute character later.

1. Command strings sent without the execute character will be stored within an

internal command buffer for later execution. When the X character is finally transmitted, the stored commands will be executed, assuming that all commands in the previous string were valid.

Commands are not necessarily executed in the order sent. In order to force a particular command sequence, the X character should be included after each com-

mand in the command string (see third programming example).

I~JTPIJT~~~ 6 ~wx~ 7 OIJTPIJT

338;”

F2K4X"

IOIJTPI~IT 7138.; c 6 ZlXFZ):” ’

OlJTP,,-f 708j 4 6 OlpMF4 9

OLITPILIT 7~33; i 6 X’ ’

! Execute single command. ! Execute multiple command string. ! Force command sequence. ! Send string without executing. ! Execute previous command string.

4-28

IEEE-488 PROGRAMMING

4.7.16 Purpose

Format Parameters

Default

Description

Y (Terminator)

Use to select the ASCII terminator sequence that marks the end of the instrument’s data string or status word.

YO CR LF Yl LF CR Y2 CR

Y3 LF Y4 No Terminator

Upon power up, or after a DCL or SDC is received, the YO terminator (CR LF) will be selected.

A terminator sequence can be programmed by sending the Y command followed

by an appropriate character. The default terminator sequence is the commonly us-

ed carriage return, line feed (CR LF) sequence (YO). Selecting the wrong terminator

for the controller could cause the bus to hang up.

The ASCII value of the CR character is 13, and the ASCII value of the LF character is 10.

Programming OIJTPIJT TOE:.; c i ‘.:I)::’ J Examples

,;,,JTP,jT 7fisi i i ‘.(,T::.::’ ?

! Terminate on LF CR. ! Restore default terminator

4-29

4.7.17

Z (Zero)

Purpose Format Parameters

Default

Description

Programming Note

Programming

Examples

Use to turn the zero feature on or off.

20 zero Off Zl Zero On

Upon power up or after the instrument receives a DCL or SDC command, the zero

feature will be off (ZO).

The When the Zl command is sent, the display will zero. If in operate, zero will be sourced to the load. The programmed reading that was displayed before sending Zl will be remembered. Thus, when ZO is sent, the reading that was remembered will again be displayed and sourced if in operate.

If Zl is sent twice or moxe consecutively while in the volts, amps or coulombs functioxq the programmed reading will be lost. Sending Zl the first time zeros the display

and stores the programmed reading. If Zl is sent again, the current reading, which

is zero will be the reading that is stored replacing the programmed reading.

Ol~TPIUT mF;j iiF2~Cf~~U10::s 5 ! Program 263

ljIJTp[JT I:ICITPIJT

7oy; i L 21>.(3 S

788; 6 6 Xi>: )

! Send Zl; zero display.

! Send ZO; restore 1OV reading.

for 1OV.

4-30

IEEE-488 PROGRAMMING

4.6 TIMING CONSIDERATIONS

A consideration for the IEEE-466 programming is transmission times of data over the bus and the time it takes for the Model 263 to perform the tasks defined by devicedependent commands.

Typically, a command string sent to the Model 263 will transmit at a rate of one character per millisecond. For example, the command string “FlZlOlX” will typically take 7msec to transmit from the controller to the Model 263.

The time it takes for the Model 263 to perform the tasks of the command string is typically 16msec. This is the time from “X” to “instrument configured”.

When the Model 263 is sending a reading to the controller,

the transmission rate will typically be one character per

0.2msec. The output of the Model 263 is refreshed once per second. Thus, the Model 263 will only place one reading per second on the bus.

4-3114-32

SECTION 5

Applications

5.1 INTRODUCTION

The applications in this section use the Model 263 as a calibrator for calibrating Keithley electrometers and picoammeters, and as a source.

The Model 263 simplifies most elecrometeripicoammeter calibration procedures. In many cases, a single Model 263 eliminrites the need for separate sources (some custom built) for voltage, current, charge and resistance.

5.1.1 Calibration Applications

Paragraphs 5.2 and 5.3 contain complete procedures for calibrating the Keithley Models 485 Picoammeter and 617 Electrometer using the Model 263. Complete, separate procedures are provided for performing digital calibration from either the front panel or over the IEEE-488 bus. Digital calibration over the IEEE-488 bus is automated using BASIC programs run by the HP 85 computer.

Paragraph 5.4 summarizes how the Model 263 can be used to calibrate the remaining Keithley picoammeterielec-

trometer product line. These products include the Models 480 Picoammeter, 619 Electrometer, 614 Electrometer, 642 Electrometer, 610C Electrometer, 602 Electrometer, and the

616 Electrometer.

Calibration of Keithley picoammeters and electrometers

should be performed when recommended by their instruc-

tion manuals, or if the performance verification procedures

in the respective instruction manuals show any to be out

of specification. If any of the calibration procedures can-

not be performed P roperly, refer to that instrument’s in-

struction manual or houbleshooting information. If the

problem persists, contact your Keithley representative or

the factory for futher information.

5.1.2 Sourcing Applications

Paragraph 5.5 contains several applications using the

Model 263 as a precision source. Application topics cover

null detection, which includes current suppression and galvanometric measurements, low ( <lOOmbl) resistance measurements, resistivity measurements, and diode characterization.

5.2 MODEL 465 CALIBRATION

The following paragraphs provide detailed procedures for calibrating the Model 485 Picoammeter using the Model 263 Calibrator/Source. All but one of the calibration ad-

justments are digital and can be done from the front panel

or over the IEEE-488 bus.

To calibrate the instrument from the front panel, perform the following procedures, omitting paragraph 5.2.5. To calibrate the Model 485 over the IEEE-488 bus, perform the following procedures, omitting paragraph 5.2.4.

5.2.1 Calibration Storage Enable

The Model 485 must be in calibration storage enable to

store calibration constants in NVRAM. is not placed in this mode, subsequent calibration will be lost when the instrument is torned off. Perform the following steps to enable calibration storage.

1. If the Model 485 is presently on, turn it off.

2. While holding in the STOKLR button, turn the instrw

ment back on.

3. When the “CAL!’ message is displayed, release the

STOKLR button. The instrument will return to the normal display mode and the storing of calibration constants is now enabled.

If the instrument

5.2.2 Required Equipment

The following items (one of each) are necessary to calibrate the Model 485:

1. Keithley Model 263 Calibrator/Source.

2. Triax to Triax Cable (supplied with 263)

3. Keithley Model 4804 Male BNC to Female Triax Adapter.

5-l

APPLICATIONS

NOTE: The following additional items will be neccesary if calibration is to be performed over the IEEE-488 bus.

4. Keithley Model 4853 IEEE-488 Interface installed in the Model 485.

5. HP 85 Computer equipped with HP 82937 Gl’IEi Inter-

face and I/O ROM.

6. Keithley Model 7008 IEEE cable.

5.2.3 Environmental Conditions

Calibration should be performed under laboratory conditions having an ambient temperature of 23 * 1°C and a relative humidity of less than 70%. With both the Model 485 and 263 on, allow them to warm up for one hour. If either instrument has been subjected to extreme temperature or humidity, allow at least one additional hour for the instrument to stabilize before beginning the calibration procedure.

NOTE

Calibration can be stopped at any time and only those ranges out of specification need be calibrated.

5.2.4 Front Panel Calibration

3. Connect the output of the Model 263 Calibrator/Source to the input of the Model 485 as shown in Figure 5-1. Make sure the calibrator is in standby,

4. On the Model 485, press the REL and LOG pushbuttons simultaneously and hold in until the message

“CAL” is displayed. Release the buttons. The unit is now in the calibration mode as indicated by the “CAL” annunciator.

5. Release ZERO CHECK on the Model 485.

6. Program the Model 263 to output .OOOOO nA. Use the AMPS (active) current source.

7. The Model 485 may be displaying a small offset (= 1 count). To cancel this offset, press REL on the Model 485 to zero the display.

8. Program the Model 263 to output 1.90000 nA.

9. Adjust the display of the Model 485 to read 1.9OOOnA using the STOiCLR and RCL buttons. The STOiCLR button increments the displayed reading and the RCL button decrements the displayed reading.

10. Using Table 5-1 as a guide, repeat the basic procedure outlined in steps 5 through 9 to calibrate the rest of the current ranges of the Model 485.

11. To store calibration constants and exit the calibration mode, simultaneously press the REL and LOG buttons until the message “Star” is displayed. If instead the message “out” is displayed, then calibration storage was not enabled as explained in paragraph 5.2.1 and calibration constants will only be valid until the Model 485 is turned off.

Perform the following steps to calibrate the Model 485 from the front panel:

1. On the Model 485, depress ZERO CHECK and select the 21~4 range.

2. With an open input, adjust the ZERO pot for .OOOO * 1 count on the display.

NOTE

If Q104, U105, R113, R114 or R115 have been replaced, the picoammeter may not zero. See paragraph 5.7 in the Model 485 Instruction Manual for the procedure to balance the input amplifier.

Table 5-l. Model 485 Range Calibration

263 Output

485 Range

2:?+

200 IIA

20 PA

200 PA

2mA

current 485 Reading

1.90000 IL4

19.0000 nA

190.000 I-LA

1.90000 fiA

19.0000 PA

1.9ooonA

19.000 IIA

190.00 nA

1.9000 pA

19.000 PA

190.000 &A 190.00 PA

1.9000 InA

1.9ooomA

5-2

MODEL 4804 BNC TO TRIAX ADAPTER

Figure 5-I. Model 485 Calibration Connections

APPLICATIONS

5.2.5 IEEE-488 Bus Calibration

Perform the following steps to calibrate the Model 485 over the IEEE-488 bus using the Model 263 Calibrator/Source.

1. Connect the Models 263 and 485 to the GLIB interface of the HP 85 computer. The Model 485 must have a Model 4853 IEEE-488 Interface installed.

2. Make sure the IEEE-488 address of the Model 263 is set to 8 and the address of the Model 4853 is set to 22.

3. Enter the calibration program into the HP 85 computer.

4. To calibrate the instrument, simply press the RUN key

on the computer. The program will prompt for the only manual adjustment and then automatically calibrate

all the current ranges of the Model 485.

5. The program will prompt for storage of the calibration constants (line 330). This provides the user the opportunity to stop at this point to avoid permanent calibration. The calibration constants will be lost when the Model 485 is turned off.

6. Storage of calibration constants is performed on line 350 of the program and is indicated by the “Star” message on the Model 485. If instead the message “out” is displayed, calibration storage was not enabled as explained in paragraph 5.2.1 and calibration constants will

be lost when the Model 485 is turned off.

7. After calibration is completed, it is recommended that you source a current from the Model 263 to each range

at k half scale to verify accuracy.

5-3

APPLICATIONS

10 CLEAR 722 @ CLEAR 2@ WPiIT 1000 30 OUTPUT 722 ;'ClRlX40 BEEP @ OISP "AOJUST 'ZERO' POT ON 485 FOR 50 DISP 60 DISP ~IF DISPLAY WILL NOT ZERO, PRO- CEED TO PARAGRAPH 5.7 IN THE 485MhNUAL. 70 DISP 80 DISP "PRESS 'CONT' 30 PAUSE

100 CLEAR @ BEEP

110 OISP "CONNECT 263 OUTPUT TO 485 INPUT (SEE FIGURE SI20 DISP

130 DISP 'PRESS 'CON?' TO CONTINUE 140 PAUSE

150 OATA 1,.Q000000013,2,.000000013,~,.00000013,4,.0000019,5,.000019,6,.00013,7, 160 CLEAR

170 CLEPlR 708

180 OUTPUT 708 i "FlR4V1.9E-9X" 190 OUTPUT 722 ?C0X' ! 485: disable 200 FOR I=4 TO 10 210 REPlO 3 220 OUTPUT 722 ;'R";J;"X" ! 485; select ranQe. 230 OUTPUT 708 ;'R";I;"X" ! 263; select ranoe. 240 OUTPUT 708 ;'ZiOlX 250 WPlIT 3000 260 OUTPUT 722 ;"ZlX" 270 READ J@ WAIT 2000 280 OUTPUT 708 i "Z0X" 230 WpiIT 2000 300 OUTPUT 722 :-U";J; 310 OUTPUT 722 i "Z0X' 320 NEXT I 330 BEEP @ DISP *TO STORE CAL CONSTPINTS, PRESS 'CONT'.' 340 PAUSE 350 OUTPUT 722 ;"L0X" ! 485: store 360 CLEAR @ BEEP 370 DISP 'ChLIBRhTION COMPLETE" 380 END

! 485; set to 2nA range and enable ZERO CHECK.

.0000 t/-l COUNT."

KEY ON THE HP 85 TOCONTINUE.'

-l).'

! 263; program for 1.9nH.

ZERO CHECK.

! 263; output zero amps.

485; enable REL to cancel offset.

263; source programmed output.

K' ! 485; send calibration value.

485; disable REL.

ca! constants

485 CALIBRATION PROGRAM

5.3 MODEL 617 CALIBRATION

The following paragraphs provide detailed procedures to calibrate the Model 617 using the Model 263 Calibrator/

Source. Most of the calibration procedures are digital in nature and can be done from the front panel or over the IEEE-488 bus.

To calibrate the instrument from the front panel, perform

5-4

the following procedures, omitting paragraph 5.3.7. To calibrate the Model 617 over the IEEE-488 bus, perform the following procedures, omitting paragraph 5.3.6.

5.3.1 Calibration Jumper

A jumper, located on the mother board, disables/enables front panel and IEEE-488 bus calibration. When the jumper is in the disabled position, permanent (NVRAM)

APPLICATIONS

storage of calibration constants will not take place. However, temporary calibration values may be entered and used even if NVRAM

calibration storage is disabled. Note, however, that calibration parameters will be lost once power is turned off unless they are stored in NVRAM.

The calibration jumper location and the disabled/enabled positions are indicated in Figure 5-2.

WARNING

Turn

off the instrument and disconnect the

cord

before removing the top cover to reposi-

line

tion the calibration jumper.

5.3.2 Required Equipment

The following items (one of each) are necessary to calibrate the Model 617:

1. Keithley Model 263 Calibrator/Source.

2. Keithley Model 196 System DMM ( f 0.015%).

3. Fluke Model 343A DC Voltage Calibrator (190V;

4. Triax-to-Triax cable (supplied with 263).

5. Keithley Model CA-18-l Dual Banana-to-Banana cable. NOTE: The following additional equipment will be

necessary if calibration is to be performed over the IEEE-488 bus.

6. HP 85 Computer equipped with HP 82937 GPIB Interface and I/O ROM.

7. Keithley Model 7008 IEEE cable.

*Accuracy requirement of calibration equipment.

5.3.3 Environmental Conditions

Figure 5-2. Calibration Jumper Location

(Model 617)

Calibration should be performed under laboratory condi-

tions having an ambient temperature of 23 f 1°C and a

relative humidity of less than 70%. With both the Models 617 and 263 on, allow them to warm up for one hour. If either instrument has been subjected to extreme temperature or humidity, allow at least one additional hour for

the instrument to stabilize before beginning the calibra-

tion procedure.

NOTE

While rated accuracy of the Model 617 is achieved after the two hour warm UD ueriod. inuut bias current may require additional tune to come to its

1 i

optimum level. Allow two hours for input bias current to settle to less than 10fA and eight hours to less than 5fA.

5.3.4 Calibration Sequence

Model 617 calibration must be performed in the order given in the following paragraphs, with the exception of the voltage source calibration, which can be done at any time. The basic sequence is:

5-5

APPLICATIONS

Manual Adjustments:

1. Input offset adjustment

2. Input current adjustment

3. Voltage source calibration adjustments

Digital Calibration (Front Panel or IEEE-488 Bus):

4. Amps calibration

5. Coulombs calibration

6. Volts calibration

7. Ohms calibration

The voltage source is calibrated third since this is a manual adjustment. This allows the digital calibration procedures to be grouped together.

In addition to the above sequence, the ranges for each function must be calibrated in the order given. Note that you should never calibrate a range using a suppress or

a zero correct value taken on a different range.

5.3.5 Manual Calibration Adjustments

2. Remove the two screws securing the top cover and remove the cover from the instrument.

3. Select the amps function and place the instrument on the 2pA range.

4. Enable zero check, but leave zero correct disabled.

5. Locate the offset adjustment pot (R314) on the electrometer board (see Figiue 53). The pot is accessible through a small hole in the shield closest to the rear of the instrument.

6. Adjust R314 for a reading of 0.0000 *l count on the display.

7. Replace the top cover unless the following input current adjustment is to be performed.

REAR PANEL

INPUTOFFSET

ADJUSTMENT

(R314)

INPUTCURRENT

ADJUSTMENT

After performing the following manual calibration ad-

justments, proceed to either front panel digital calibration

(paragraph 5.3.6) or IEEE-U Bus Digital Calibration (paragraph 5.3.7).

A. Input Offset Adjustment Perform the following steps to null out any small offset

in the input amplifier:

1. Disconnect all input signals from the Model 617.

ELECTROMETER

BOARD

FRONT PANEL

Figure 5-3. Input Offset Adjustment Locations

(Model 617)

5-6

APPLICATIONS

B. Input Current Adjustment Use the following procedure to null out any input current

in the input stage:

1. Disconnect all input signals from the Model 617. Place the protection cap (CAP-B) on the INPUT connector.

2. Remove the two screws securing the top cover and remove it from the instrument.

3. Place the Model 617 in the amps function and the 2pA

range.

4. Enable zero check and zero correct in that order.

5. Disconnect floating sources and connect a ground link

between the COM and chassis ground binding posts. Disable zero check, but leave zero correct enabled.

6. Wait several minutes until the reading on the display

settles down; about 15 counts (1.5fA) p-p of noise is normal.

7. Locate the input current pot R348 on the electrometer

board. It is accessible through a small hole in the shield

(see Figure 5-3).

8. Carefully adjust R348 for a reading of 0.0000 115 counts

on the display. Iterative adjustment may be necessary.

9. Replace the top cover and secure it with the two screws

removed earlier.

source. Since the voltage source is independent from the electrometer section, voltage source calibration can be performed at any time.

WARNING

Hazardous voltage will be used in some of the

following steps.

1. Connect the Model 196 DMM to the voltage source out-

put as

shown in Fimre 5-4.

2. From the front panei program the voltage source of the Model 617 to O.OOV.

3. Turn on the voltage source output by pressing the

OPERATE button.

4. Place the Model 196 in autorange and note the offset voltage value. A reading of 50mV OI less should be

displayed.

5. Press ZERO on the Model 196 to cancel the offset.

6. Program the Model 617 to output lOO.OOV.

7. Adjust the voltage source gain adjustment (see Figure 5-4) so that the DMM reads a voltage of 1OOV f 10mV.

8. Turn off the voltage source output and disconnect the DMM.

C. Voltage Source Calibration Use the following procedure to calibrate the voltage

VOLTS OHMS

VOLTAGE SOURCE GAIN ADJUSTMENT

Figure 5-4. Connections for Model 617 Voltage Source Calibration

5.3.6 Front Panel Digital Calibration

Perform the following procedures to digitally calibrate the Model 617 from the front panel.

DUAL BANANA CABLE

(MODELCA-18-l)

5-7

Keithley 263 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual