Keithley 617 Service manual

Model 617

Programmable Electrometer

Instruction Manual

Contains Operating and Servicing Information

WARRANTY

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

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

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

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

LIMITATION OF WARRANTY

This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or misuse of

any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from battery leakage, or

problems arising from normal wear or failure to follow instructions.

THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PROVIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.

NEITHIZR KEITHLEY INSTRUMBNTS, 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

SOmWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.

Keithley Instruments, Inc. - 28775 Aurora Road - Cleveland, OH 44139 - 216-248-0400 - Fax: 216-24X-6168 - http://www.keithley.com

Model 617 Programmable Electrometer

Instruction Manual

0 1984, Keithley Instruments, Inc.

Test Instrumentation Group

Cleveland, Ohio, U.S.A.

Document Number: 617-901-01 Rev. C

SPECIFICATIONS

TABLE OF CONTENTS

SECTION l-GENERAL INFORMATION

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

1.10

1.11

1.12

2.1

2.2

2.3

2.4

2.4.1

2.4.2

2.4.3

2.5

2.5.1

2.5.2

2.5.3

2.6

2.6.1

2.6.2

2.6.3

2.7

2.7.1

2.7.2

2.7.3

2.7.4

2.7.5

2.7.6

2.7.7

2.7.8

2.8

2.8.1

2.8.2

2.9

2.9.1

2.9.2

2.10

2.10.1

2.10.2

2.10.3

2.10.4

2.10.5

2.10.6

Introduction

Features ...................

Warranty Information ManualAddenda.. Safety Symbols and Terms Specifications Using this Instruction Manual Unpacking and Inspection Getting Started Preparation for Use Repacking for Shipment. Accessories

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SECTION 2-OPERATION

Introduction Power Up Procedure Power Up Self Test and Display Messages Front Panel Familiarization

Controls Display and Indicators TiltBan

Front Panel Programs

IEEE-488 Address Exponent Mode (Alpha or Numeric) Calibration

Rear Panel Familiarization.

Connectors and Terminals.

V,RGUARDSwitch

LineFuse..

Basic Measurement Techniques.

Warm Up Period Input Connections Making Voltage Measurements. Guarded Operation Making Current Measurements. Making Charge Measurements Resistance Measurements Using the Ohms Function As A Current Source

Using the Voltage Source

Basic Operating Procedure V/I Resistance Measurements

Analog Outputs

2v Analog Output PreampOut

Using External Feedback

Electrometer Input Circuitry

Shielded Fixture Construction External Feedback Procedure. Non-Standard Coulombs Ranges Logarithmic Currents Non-Decade Current Gains

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....... 2-2

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....... 2-7

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.. ...

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...... 2-17

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2-l 2-l 2-l

2-2 2-4 2-4 2-4 2-4 2-5 2-5 2-5 2-5 2-7 2-7

2-7 2-8

2-E Z-10 2-11 2-13 2-15 2-16 2-17

2-17 2-19 2-19 2-19 2-22 2-22 2-22 2-23 2-24 2-24 2-2.5

2.11

2.11.1

2.11.2

2.12

2.13

2.13.1

2.13.2

2.13.3

2.14

2.14.1

2.14.2

2.14.3

2.14.4

2.14.5

2.14.6

2.14.7

2.14.8

2.15

Using Zero Correct and Baseline Suppression

Zero Correct and Zero Check

Using Suppression ......................

DataStorage .............................

External Triggering. .......................

External Trigger ........................

Meter Complete ........................

Triggering Example .....................

Measurement Considerations ...............

GroundLoops

Electrostatic Interference .................

Thermal EMFs .........................

RF1 ...................................

Leakage Resistance Effects ................

Input Capacitance Effects. ................

Source Resistance .......................

Source Capacitance .....................

Engineering Units Conversion ...............

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SECTION 3-IEEE-488 PROGRAMMING

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.......

3.1

3.2

3.3

3.3.1

3.3.2

3.3.3

3.4

3.4.1

3.4.2

3.4.3

3.4.4

3.4.5

3.5

3.4

3.6.1

3.6.2

3.6.3

3.7

3.7.1

3.7.2

3.7.3

3.7.4

3.8

3.8.1

3.8.2

3.8.3

3.8.4

3.9

3.9.1

3.9.2

3.9.3

3.9.4

3.9.5

3.9.6

3.9.7

3.9.8

3.10

Introduction

BusDescription

IEEE-488BUSLINES ..........................................................................

DataLines..

BusManagementLines ...........................................

HandshakeLines

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

UniIineCommands

UniversalCommands ........................................................................

AddressedCommands .......................................................................

Unaddressedcommands .....................................................................

Device-DependentCommands

CommandCodes.. ...........................................................................

CommandSequences ..........................................................................

AddressedCommandSequence

UniversalCommandSequence

Device-DependentCommandSequence

Hardwareconsiderations.. ....................................................................

Typical Controlled Systems. ..................................................................

BusConnections ............................................................................

PrimaryAddressProgramming ...............................................................

Talk-OnlyMode

Softwareconsiderations

Controller Handler Software,

Interface BASIC Programming Statements

Interface Function Codes

IEEECommandGroups

General Bus Command Programming

REN(RemoteEnable) .......................................................................

IFC(InterfaceClear)

LLO(LocalLockout) .......................................................

GTL(GoToLocaI)

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

SDC (Selective Device Clear)

GET(GroupExecuteTrigger). ...............................................................

Serial Polling (WE, SPD)

Device-Dependent Command Programming

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................................................... 3-10

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

..r

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............................. 3-16

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

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.._

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

3-2 3-3

3-3 3-4 3-4 3-5 3-5 3-5 3-5 3-5 3-7 3-7 3-7 3-7 3-8 3-9

3-10 3-10

3-12 3-12

3-12 3-13 3-14 3-14

3-14

3-15

3-16

3-17

3.10.1

3.10.2

3.10.3

3.10.4

3.10.5

3.10.6

3.10.7

3.10.8

3.10.9

3.10.10

3.10.11

3.10.12

3.10.13

3.10.14

3.10.15

3.10.16

3.10.17

3.10.18

3.11

3.11.1

3.11.2

3.11.3

3.12

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

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

Range(R) Zero Correct and Zero Check (Z and C)

Baseline Suppression (N) .............

Display Mode CD).

Reading Mode (B) ............ ......

Data Store Mode ...................

Voltage Source Value (V) .............

Voltage Source Operate (0) ..........

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

Non-Volatile Memory Storage (L) .....

Data Format (G) ....................

Trigger Mode (T) ...................

SRQ Mode (M) and Status Byte Format

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

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

Status(u) .........................

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

BusError.. ........................

NumberError ......................

Trigger Overrun Error ...............

Bus Data Transmission Times ...........

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

SECTION 4-APPLICATIONS

3-18

3-20

3-21

3-22

3-23

3-24

3-25

3-26

3-27

3-28

3-30

3-31

3-34

3-35

3-36

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10

5.1

5.2

5.3

5.4

5.5

5.5.1

5.5.2

5.5.3

5.5.4

5.5.5

5.5.6

5.5.7

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

Insulation Resistance Measurements.

HighImpedanceVoItmeter

Low-Level Leakage Current Measurements DiodeCharacterization CapacitorLeakageMeasurements CapacitanceMeasurement Voltage Coefficients of High-Megohm Resistors

Static Charge Detection ........................................................

Using the Model 617 with External Voltage Sources

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SECTION 5-PERFORMANCE VERIFICATION

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

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

Initial Conditions ..........................

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

Verification Procedure ......................

Input Current Verification .................

Amps Verification .......................

Coulombs Verification. ...................

Volts Verification ........................

Ohms Verification .......................

Ohms Verification (200M0 and Gfl Ranges)

Voltage Source Verification. ...............

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4-l 4-l 4-5 4-5 4-7 4-8

4-E 4-10 4-12 4-12

5-l

5-2

5-2 5-3 5-5 5-6 5-6 5-8

iii

SECTION 6-THEORY OF OPERATION

6.1

6.2

6.3

6.3.1

6.3.2

6.3.3

6.3.4

6.3.5

6.4

6.4.1

6.4.2

6.4.3

6.5

6.6

6.6.1

6.6.2

6.6.3

6.6.4

6.6.5

6.6.6

6.7

6.6

7.1

7.2

7.3

7.3.1

7.3.2

7.4

7.4.1

7.4.2

7.4.3

7.4.4

7.4.5

7.4.6

7.4.7

7.4.8

7.4.9

7.4.10

7.4.11

7.4.12

7.4.13

7.4.14

7.4.15

7.4.16

7.5

7.6

7.7

7.7.1

7.7.2

7.7.3

7.7.4

7.7.5

7.7.6

Introduction Overall Functional Description Input Preamplifier

Input stage ......................

Gain Stage. ......................

Output stage. ....................

Ohms Voltage Source

Zero Check ......................

Additional Signal Conditioning

Ranging Amplifier ................

Multiplexer and Buffer Amplifier ....

- 2V Reference Source. ............

A/D Converter. Digital Circuitry

Microcomputer. ..................

Memory Elements. ................

Device Selection ..................

IEEE-486 Bus .....................

Input/Output Circuitry ............

Display Circuitry .................

Voltage source Power Supplies

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SECTION 7-MAINTENANCE

Introduction..

LineVoltageSelection

FuseReplacement

Lim Fuse .................................................................................

COMFuse ................................................................................

Calibration

Recommended Calibration Equipment. ........................................................

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

WarmUpPeriod ..........................................................................

CalibrationJumper

Front Panel Calibration .....................................................................

IEEE-488 Bus Calibration. ...................................................................

Calibration Sequence .......................................................................

InputOffsetAdjustment ....................................................................

InputCurrentAdjustment ...................................................................

Pemxnent Storage of Calibration Parameters

AmpsCalibration.. .......................................................................

Coulombs Calibration ...................................................................

VoltsCalibration.. ........................................................................

OhmsCalibration .........................................................................

Voltage Source Calibration ..................................................................

Additional Calibration Points ................................................................

Special Handling of Static-Sensitive Devices Disassembly Instructions Troubleshooting

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

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

SelfDiagnosticProgram ....................................................................

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

RelayConfiguration ........................................................................

Ranging Amplifier Gain Configuration ........................................................

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6-l

6-1 6-l 6-3 6-3 6-3 6-6 6-7 6-7 6-7 6-8 6-9

6-9 6-11 6-11

6-11 6-u

6-11 6-12 6-12 6-13 6-14

7-l

7-1

7-2

7-Z

7-2

7-2 7-3 7-3 7-3 7-3 7-4 7-5 7-5 7-s 7-6 7-4 7-7 7-8

7-a 7-10 7-10 7-U 7-12 7-12 7-12 7-14 7-14

7-14 7-15 7-15

7.7.7

7.7.8

7.7.9

7.7.10

7.7.11

7.8

7.9

A/DConverterandDisplay .................................

Input and Ranging Amplifiers

DigitalCircuitry.. .................................................

Display Board

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

InputStageBalancingProcedure Handling and Cleaning Precautions

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SECTION 8--REPLACEABLE PARTS

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... 7-16

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... 7.17

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7.17

7-17 7-17 7-17 7-18

8.1

8.2 a.3 a.4 a.5

8.6

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

Electrical Parts Lists Mechanical Parts Ordering Information Factory Service.. Component Layout Drawings and Schematic Diagrams

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......

8-l 8-l 8-l 8-l 8-l 8-l

LIST OF ILLUSTRATIONS

2-l 2-2 2-3 2-4 2-5 2-6 2-7 2-a 2-9 2-10 2-11 Z-12 2-13 2-14 2-15 2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23 2-24 2-25 2-26 2-27 2-28 2-29

Model617FrontPanel..........................................

Model617RearPanel Input Connector Configuration Connections For Voltage Measurements

Meter Loading Considerations Unguarded Circuit

GuardedCircuit Guarded Input Connections CurrentMeasurements Voltage Burden Considerations. Coulombs Connections Resistance Measurement Connections Voltage Source Connections V/l Resistance Measurement Connections Typical 2V Analog Output Connections Typical Preamp Out Connections. Electrometer Input Circuitry (AmpsMode) Shielded Fixture Construction

“Transdiode” Logarithmic Current Configuration Non-Decade Current Gains Equivalent Input Impedance with Zero Check Enabled. External Trigger Pulse Specifications Meter Complete Pulse Specifications Exlemal Triggering Example Multiple Ground Points Create Ground Loop Eliminating Ground Loops Leakage Resistance Effects Input Capacitance Effects. Simplified Model of Source Resistance and Source Capacitance Effects

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2-2 2-7

2-8

2-9

2-10

2-13 2-13 2-14 2-16 2-17 2-18

2-31 2-33

2-34 2-34

3-l IEEE Bus Configuration 3-2 3-3 3-4 3-5 3-6 3-7 617 Rear Panel IEEE Connector. 3-B Contact Assignments 3-9 General Data Format 3-10 SRQ Mask and Status Byte Format. 3-11 UO Status Word and Default Values. 3-12 3-13 U2 Status (Data Condition) Format

IEEE Handshake Sequence. Commands Groups System Types IEEE-488 Connector IEEE-488 Connections

Ul Status (Error Condition) Format

.......

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

4-9 4-10 4-11 4-12

Insulation Resistance Measurement (Ungaurded)

..........

Insulation Resistance Measurement (Guarded) ............

Insuiation Resistance Measurement Using V/I Ohms Mode.

Measuring High Impedance Gate-Source Voltage ..........

Leakage Current Measurement .........................

Diode Characterization ...............................

DiodeCurves.. .....................................

Capacitor Leakage Tests

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

Capacitor Measurement. ..............................

Configuration for Voltage Coefficient Studies ...........

Farady Cup Construction .............................

Using the Model 617 with an External High Voltage Source

......

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

6-l 6-2 6-3

b-4 b-5 6-b

6-7 6-8 6-9

6-10

6-11

6-12 b-13

b-14

b-15

6-16

Test Fixture Construction

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

Connections for Amps Verification (200nA-2mA Ranges) ...........

Connections for Amps Verification (2pA-20nA Ranges) ............

Connections for Coulombs Verification ..........................

Connections for Volts Verification

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

Connections for Ohms Verification (2kQ-20MQ Ranges) ............

Connections for Ohms Verification (200MR. 2G0 and 20Gfl Ranges).

Input Impedance Verification ..................................

Connections for Voltage Source Verification ......................

Overall Block Diagram ............................

Basic Configuration Electrometer Preamplifier

.........

Electrometer Preamplifier Configuration ..............

Simplified Schematic of Input Stage

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

GainStage .......................................

Output Stage Configuration (Volts and Ohms) .........

Output Stage Configuration (Amps and Coulombs)

.....

Ohms Voltage Source Simplified Schematic ...........

Zero Check Configuration (Volts and Ohms) ..........

Zero Check Configuration (Amps and Coulombs) ......

Simplified Schematic of Ranging Amplifier ............

Multiplexer and Buffer

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

Multiplexer Phases ...............................

-2V Reference Source.

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

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

Simplified Schematic of Voltage Source Output Stage ...

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.., ..,

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

6-2 6-3 b-4

b-5

6-5 6-5

6-b

b-6 b-7

6-7

b-8

6-8 6-9 6-9

b-10

6-13

7-l 7-2 7-3 7-4 7-5

7-6 7-7 7-8 7-9 7-10 7-11

Test Fixture Construction .......................................

Calibration Jumper Location .....................................

Input Offset Adjustment Locations.

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Connections for Amps Calibration (20pA Range) ....................

Connections for Amps Calibration (20nA. 20/rA and 20mA Ranges)

Connections for Coulombs Calibration ............................

Connections for Volts Calibration ................................

Connections for Ohms Calibration (20GQ and 2OOMO Ranges) .........

Connections for Ohms Calibration (2Ok%ZOMQ) Connections for Voltage Source Calibration

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Model617ExplodedView .......................................

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7-l 7-3

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

7-9 7-10 7-10 7-13

vii

8-l Electrometer Board, Component Location Drawing. g-2 8-3

Mother Board, Component Location Drawing

Display Board, Component Location Drawing 8-4 Electrometer Board, Schematic Diagram 8-5

Mother Board, Schematic Diagram. 8-6 Display Board, Schematic Diagram

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8-11

g-13 8-17 8-19

8-21 8-27

. .

LIST OF TABLES

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

2-11

3-l 3-2 3-3

3-4

3-5

3-6 3-7 3-a 3-9 3-10

3-11

3-12

3-13 3-14 3-15

Display Error Messages .................................

Front Panel Program Messages

Typical Display Exponent Values ................

Ohms Function Current Output Values

Typical 2V Analog Output Values ........................

Full Range PREAMP OUT V&es ......

Data Store Reading Rates ...........

Voltage and Percent Error For Various Time Constants Minimum Recommended Source Resistance Values in Amps. ..

Engineering Units Conversion ..................

Equivalent Voltage Sensitivity of 617 Amps Ranges

IEEE-488 Bus Command Summary. .........................

Hexadecimal and Decimal Command Codes Typical Addressed Command Sequence

Typical Device-Dependent Command Sequence.

IEEE Contact Designations ................................

BASIC Statements Necessary to Send Bus Commands

Model 617Interface Function Codes. ........................

IEEE Command Groups. General Bus Commands and Associated BASIC Statements Default Conditions.

Device-Dependent Command Summary

Range Command Summary ...............................

SRQ (M) Command Parameters ............................

Bus Hold-Off Times

Typical Bus Times For Various Functions and Trigger Modes

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...

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3-4

3-5 3-7 3-7

3-9

3-11 3-12 3-13 3-13 3-15

3-19 3-21

3-28 3-31 3-36

4-l

5-l

5-2 5-3 5-4 5-5 5-6

6-l

Diode Currents and Voltages.

Recommended Test Equipment for Performance Verification Limits for A mps Verlflcatlon Limits for Volts Verification Limits for Ohms Verification (2kn-2OMa Ranges). Limits for Ohms Verification (2COMn, 2Gn and 2OOGil Ranges) Voltage Source Verification Limits

MemoryMapping .._......................................................

......

4-7

5-l 5-3 5-5

5-b

5-7 5-8

6-11

7-1 7-2 7-3 7-4 7-5 7-6 7-7 7-8 7-9 7-10 7-11 7-12 7-13 7-14 7-15 7-16 7-17 7-18 7-19

8-l a-2 8-3

8-4

Line Voltage Selection (50-60Hz). LineFuseSelection

Recommended Calibration Equipment

AmpsCalibration .............................................................................

VoltsCalibration..

OhmsCalibration .............................................................................

StaticSensitiveDevices

Recommended Troubleshooting Equipment DiagnosticProgramPhase PowerSupplyChecks Relayconfiguration Ranging Amplifier Gains

A/DConverterChecks

Preamplifierchecks .......................................................................... 7-19

RangingAmplifierChecks.......................................................................7-1 9

DigitalCircuitryChecks

DisplayBoardChecks

VoltageSourceChecks

InputStageBalancing .........................................................................

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

DisplayBoard,PartsList

Electrometer Board, Parts List Mechanicall’artsList

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.......................................................................... 7-16

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........................................................................ 7-21

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..................................................................... 7-15

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7-l 7-2

7-2

7-7 7-8

7-9 7-11 7-14

7-15

7-17 7-18

7-20 7-20

7-21

8-2

8-6

8-7 S-10

SAFETY PRECAUTIONS

The following safety precautions should be observed before operating the Model 617

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

Exercise extreme caution when a shock hazard is present at the instrument’s input. The American National Standards Institute (ANSI) states that a shock hazard exists when voltage levels greater than 30V rms or 42.4V peak are present. A good safety practice is to expect that a hazardous voltage is present in any unknown circuit before measuring.

Do not exceed 5oOV peak between input low and earth ground. Do not connect PREAh4P OUT, COM, OI 2V ANALOG OUTPUT to earth ground when floating input.

Inspect the test leads for possible wear, cracks or breaks before each use. If any defects are found, replace with test leads that have the same measure of safety as those supplied with the instrument.

For optimum safety do not touch the test leads or the instrument while power is applied to the circuit under test. Turn the power off and discharge all capacitors, before connecting or disconnecting the instrument.

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

Do not exceed the instrument’s maximum allowable input as defined in the specifications and operation section.

Safe operation and good measurement practice dictates use of an external resistor when necessary to limit input currents to less than 30mA.

SECTION 1

GENERAL INFORMATION

1.1 INTRODUCTION

The Keithley Model 617 Programmable Electrometer is a

highly sensitive instrument designed to measure voltage, current, charge, and resistance. Two forms of resistance measurements are included in the standard configuration: a constant current method, and a constant voltage method that uses a built in voltage source for greater sensitivity. The measuring range of the Model 617 is between 1OpV and 200V for voltage measurements, O.lfA and 2OmA in the current mode, O.ln and 200GO (up to 1OlQ using the built in voltage source), and lOfC and 20°C in the coulombs mode. The very high input impedance and extremely low input offset current allow accurate measurement in situations where many other instruments would have detrimental effects on the circuit being measured. A 4% digit display and standard IEEE-488 interface give the user easy access to instrument data.

1.2 FEATURES

Some important Model 617 features include:

l 4% Digit Display-An easy to read front panel LED display

includes a 4% digit mantissa plus a two-digit alpha or

numeric exponent.

l Autoranging-Included for all functions and ranges. l Digital Calibration-The instrument may be digitally

calibrated from the front panel or over the IEEE-488 bus.

l Zero Correct-A front panel zero correct control allows the

user to cancel any offsets.

l Baseline Suppression-One button suppression of a

baseline reading is available from the front panel or over the

IEEE-488 bus.

l One-shot Triggering-A front panel control for triggering

one-shot readings from the front panel is included.

l Isolated IOOV Voltage Source-A built in 1OOV scwrce is

isolated from the electrometer section. The voltage source is

programmable in 50mV steps.

l Selectable Guarding-A selectable driven cable guard is in-

cluded to optimize speed.

l Standard IEEE-488 Interface-The interface allows full bus

programmable operation of the Model 617.

l Analog Outputs-Both preamp and 2V full range analog

outputs are included on the rear panel.

l 100~Point Data Store-An internal buffer that can store

up to 100 readings is accessible from either the front panel or over the IEEE-488 bus.

l Minimum and maximum data points can be stored and are

accessible from the front panel or over the IEEE-488 bus.

1.3 WARRANG INFORMATION

Warranty information for your Model 617 may be found inside the front cover of this manual. Should you need 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, Great Britain, France, the Netherlands, Switzerland, and Austria. Information concerning the operation, application, or service of your instrument may be obtained from the applications engineer at any of these locations.

1.4 MANUAL ADDENDA

Information concerning improvements or changes to the instrument which occur after the printing of this manual will be found on a” addendum sheet included with this manual. Please be sure that you read this information before attempting to operate or service your instrument.

1.5 SAFETY SYMBOLS AND TERMS

The following safety symbols and terns are used in this

manual and found on the instrument:

The A should refer to the operating instructions in this manual for

further details.

The WARNING heading as used in this manual explains dangers that might result in personal injury or death. Always

read the associated information very carefully before performing the indicated procedure.

The CAUTION heading used in this manual explains hazards

that could damage the instrument. Such damage may in-

validate the warranty.

symbol on the instrument indicates that the user

l-l

1.6 SPECIFICATIONS

The following items aw included with every Model 617 shipment:

Detailed Model 617 specifications may be found immedi-

ately preceding the table of contents of the manual. Note that accuracy specifications assume that the insinxnent has been properly zero corrected, as discussed in Section 2.

1.7 USING THIS INSTRUCTION MANUAL

This manual contains all the information necessary for you to

operate and service your Model 617 Programmable Elec-

trometer. The manual is divided into the following sections:

l Section 1 contains general information about your instru-

ment including that necessary to unpack the instrument and

get it operating as quickly as possible.

l Section 2 contains detailed operating information on how to

use the front panel controls and programs, make connec-

tions, and basic measuring techniques for each of the

available measuring functions.

l Information necessary to connect the Model 617 to the

IEEE-488 bus and program operating modes and functions from a controller is contained in Section 3.

l Typical applications for the Model 617 are included ‘in Sec-

tion 4. At least one application for each of the measuring

functions is included in this section.

l Performance verification procedures for the instrument

may be found in Section 5. This information will be helpful

if you wish to verify that the instrument is operating in

compliance with its stated specifications.

l Section 6 contains a complete description of operating

theory for the Model 617. Analog, digital, power supply,

and IEEE-488 interface operation is included.

l Should your instrument ever require servicing, refer to the

information located in Section 7. This section contains in-

formation on fuse replacement, line voltage selection,

calibration. and troubleshooting.

l Replacement parts may be ordered by using the information

contained in Section 8. Parts lists as well as schematic

diagrams and component layouts are located in this section.

1.8 UNPACKING AND INSPECTION

The Model 617 Programmable Electrometer was carefully in-

spected before shipment. Upon receiving the instrument,

carefully unpack all items from the shipping carton and check

for any obvious signs of physical damage that might have oc-

curred during shipment. Report any damage to the shipping

agent at once. Retain the original packing material in case

reshipment becomes necessary.

Model 617 Programmable Electrometer Model 617 Instruction Manual. Model 6011 Triaxial Input Cable Additional accessories as ordered

If an additional instruction manual is required, order the manual package (Keithley Part Number 617-901-W). The

manual package includes an instruction manual and all perti-

nent addenda.

1.9 GElTING STARTED

The Model 617 Programmable Electrometer is a highly

sophisticated instrument with many capabilities. Although there are a number of complex aspects about the instrument,

you can use the following procedure to get your instrument

up and running quickly. For more detailed information, you should consult the appropriate section of the manual.

Carefully unpack your instrument as described in paragraph 1.8.

Locate the power cord and plug it into the rear panel power jack. Plug the other end of the line cord into an appropriate power source. See Section 2 for more complete information.

Connect the supplied triaxial cable to the rear panel input jack. Make sure the rear panel V, R GUARD switch is in the off position.

Press in the front panel POWER switch to apply power to the instrument. The instrument will power up the the autorange volts mode with zero check enabled. Thus, you could simply connect the red and black input leads to a voltage source and take a voltage reading at this point by disabling zero check. Remember that the Model 617 measures DC voltages up to 2COV.

To change to a different measuring function, simply press the desired function button. For example, to measure resistance. simply press the OHMS button.

Complete detailed operation concerning Model 617 front panel operation may be found in Section 2. If you wish to control these functions over the IEEE-488 bus, consult Section 3.

1.10 PREPARATION FOR USE

Once the instrument is unpacked, it must be connected to an

appropriate power source as described below.

l-2

Line Power-The Model 617 is designed to operate from 105-125V or 210-250V power sources. A special power transformer may be installed for 90-1lOV and 195-235V ranges.

The factory set range is marked on the rear panel of the in-

strurnent. Note that the line plug is designed to mate with the

supplied 3-wire power cord.

CAUTION Do not attempt to operate the instrument on a supply voltage outside the indicated range, or instrument damage might occur.

Line Voltage Selection-The operating voltage of the instrument is internally selectable. Refer to Section 7 for the procedure to change or verify the line voltage setting,

Line Frequency-The Model 617 may be operated from either 50 or 60Hz power sources.

IEEE-488 Primary Address-If the Model 617 is to be programmed over the IEEE-488 bus, it must be set to the arrect primary address. The primary address is set to 27 at the factory, but it may be programmed from the front panel as described in Section 3.

1.11 REPACKING FOR SHIPMENT

Before shipping, the instrument should be carefully packed in its original packing material.

Model 6011 and 6011-10 Triaxial Cables-The Model 6011 is made up of 3 feet of triaxial cable that is terminated with a

trim plug on one end and 3 alligator clips on the other end. The Model 6011-10 is a similar cable 10 feet in length. Note that the Model 6011 is supplied with the Model 617.

Model 6012 Triax to UHF Adapter-The Model 6012 allows

the Model 617 to be used with accessories having UHF type co”nectors.

Model 6lOlA Shielded Test Lead-The Model 610lA is a straight through probe and shielded lead equipped with 0.8m

(3O”) of shielded low noise cable terminated by a Tefloninsulated UHF connector. The Model 6012 must be used to adapt the Model 6101A to the Model 617 triaxial input.

Model 6103C Voltage Divider Probe-The Model 6103C extends Model 617 voltage measurement range to 30kV. The Model 6103C has a division ratio of 1OOO:l with a nominal accuracy of 5%. The probe has an input resistance of 4.5 x 10110 and is equipped with a UHF male plug. The Model 6012 adapter must be used to connect the Model 6103C to the Model 617.

Model 6104 Test Shield-The Model 6104 facilitates resistance, voltage, or current measurements with either 2- or 3-terminal guarded connections at voltages up to 1200V. The Model 6104 provides excellent electrostatic shielding and high isolation resistance. Clips plug into banana jacks, allowing custom connections. The Model 6104 has a BNC camector on one side and binding posts on the other. The Model 6147 adapter (below) is required to connect the Model 6104 to the

Model 617.

If the instrument is to be returned to Keithley Instruments for repair or calibration, include the following:

Write ATTENTION REPAIR DEPARTMENT on the shipping label.

Include the warranty status of the instrument. Complete the service form at the back of this manual.

1.12 ACCESSORIES

The following accessories are available to enhance Model 617

capabilities.

Models 1019A and 1019s Rack Mounting Kits-The Model

1019A is a fiied or stationary rack mounting kit with two front panels provided to enable either single or dual side-byside mounting of the Model 617 or other similar Keithley instrument. The Model 1019s is a similar rack mounting kit with a sliding mount configuration.

Model 6105 Resistivity Chamber-The Model 6105 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 high-voltage supply such as the Model 247 as well as the Model 617. Volume resistivity up to 105Q/cm and surface resistivity up to 1018Q can be measured in accordance with ASTM test procedures. Sheet samples 64 to 102mm (2Yz X 4”) in diameter and up to 6.4mm (IA”) thickness can be accommodated. Excitation voltages up to 1OOOV may be used.

Model 6146 Triax Tee Adapter-The Model 6147 allows the simultaneous connection of two triaxial cables to the single triaxial input of the Model 617.

Model 6147 Triax to BNC Adapter-The Model 6147 allows the Model 617 input to be connected to accessories having BNC connectors.

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

1-3

Model 7008 IEEE-488 Cables-The Model 7008 cables are designed to connect the Model 617 to the IEEE-466 bus and are available in two similar versions. The Model 7008-3 is

0.9m (3 ft.) in length, while the Model 7008-6 is 1.&n (6 ft.) long. Each cable is terminated with a standard IEEE-488 connector on each end, and each connector is equipped with two metric SCTBWS.

Model 7024 Triaxial Cables-The Model 7024 cables are similar units with male triaxial connectors on each end. The Model 7024-l is 0.3m (1 ft:) in length, while the Models

7024-3 and 7024-10 are 0.9m (3 ft.) and 3.0m (10 ft.) long

respectively. These cables may be used to connect the Model 617 signal input to other equipment having similar triaxial connections.

Model 7023 Female Triaxial Connector-The Model 7023 is a

chassis mount connector that mates with the Models 6011 and 7024 triaxial cables.

Model 8573 IEEE-488 Interface for the IBM PC-The Model 8573 allows the Model 617 to be connected to and controlled from the IBM PC via the IEEE-488 bus.

1-4

SECTION 2

OPERATION

2.1 INTRODUCTION

Operation of the Model 617 may be divided into two general categories: front panel operation and IEEE-488 bus operation. This section contains information necessary to use the instrument on a front-panel basis. Note that many of these func-

tions can also be programmed over the IEEE-488 bus, as described in Section 3.

The following paragraphs contain a complete description of Model 617 front panel operation. First a complete description of each front and rear panel function is presented. Next the complete procedure for each of the measuring functions is presented, followed by a description of the built in voltage source. Finally, the analog output and guard functions are

described along with a method to apply external feedback.

2.2 POWER UP PROCEDURE

Use the procedure below to connect the Model 617 to line

power and power up the instrument.

1. Connect the female end of the power cord to the AC receptacle on the rear panel of the instrument. Connect the other

end of the cord to a grounded AC outlet.

switch. The switch will be at the inner most position when the instrument is turned on.

3. The instrument will power up in the volts function, in the autorange mode aqd with zero check enabled, as indicated by the associated front panel LEDs. All other LEDs will be off when the instrument is first turned on.

2.3 POWER UP SELF TEST AND DISPLAY MESSAGES

The RAM memory is automatically tested as part of the power up procedure. If a RAM memory error occurs, the “rr” message will remain on the display. If the instrument was not able to read the stored calibration constants and configuration, the decimal points in the two exponent digits will flash.

If such errors occur, the instrument may be partially or completely inoperative. Refer to Section 7 for more complete details.

A power up self test may be run and the software revision

level may be displayed by pressing and holding the TRIG but-

ton when the unit is first turned on. During the test, all front panel LEDs and the display segments will turn on as in the example below:

WARNING

The Model 617 is equipped with a 3-wire

power cord that contains a separate ground

wire and is designed to be used with

grounded outlets. When proper connec-

tions are made, instrument chassis is con-

nected to power line ground. Failure to use a grounded outlet may result in personal in-

jury or death because of electric shock.

CAUTION Be sure that the power line voltage agrees with the indicated range on the rear panel of the instrument. Failure to observe this precaution may result in instrument damage. If necessary, the line voltage may be changed as decribed in Section 7.

2. Turn on the power by pressing in the front panel POWER

The instrument will then display the software revision level when TRIG is released, for example:

E.4

The instrument will then enter the diagnostic mode, which is used as an aid in troubleshooting problems within the instrument. See Section 7 for details. The power must be turned off to remove the instrument from the diagnostic mode.

NOTE

If the instrument is still under warranty (less than one year from the date of shipment), and problems develop, it should be returned to Keithley Instruments for repair. See paragraph

1.11 for details on returning the instrument.

2-I

Figure 2-1. Model 617 Front Panel

PROGRAM PROGRAM

SELECT EXIT SELECT EXIT

0 0

i, i,

2.4 FRONT PANEL FAMILIARIZATION

The front panel layout of the Model 617 is shown in Figure 2-1. The front panel may be divided into two sections: controls and display indicators. The following paragraphs describe each of these items in detail.

2.4.1 Controls

All front panel controls except POWER are momentary con-

tact switches. Many control buttons include an annunciator light to indicate the selected mode. Some buttons have a secondary function that is entered by pressing the SHIFT button before pressing the desired button. All such buttons (except ADJUST) are marked in yellow. The controls are color coded into functional groups for ease of operation.

POWER-The POWER switch controls AC power to the in-

strument. Depressing and releasing the switch once turns the power on. Depressing and releasing the switch a second time turns the power off. The correct positions for on or off are marked on the front panel immediately above the POWER switch.

SHIFT-The SHIFT button adds a secondary function to some of the other front panel controls, including VOLTS, TRIG, OHMS, RECALL and PROGRAM SELECT. Note

that the shift function is entered by pressing SHIFT before the

second button rather than pressing the two simultaneously.

ELECTROMETER-The ELECTROMETER buttons control

the measuring functions, selection of instrument ranges, and such items as zero check, zero and suppression, and front panel triggering.

VOLTS-The VOLTS button places the instrument in the DC

volts measuring mode. When VOLTS is pressed, the indicator next to the button turns on, showing that the instrument is set

for that mode. Note that the Model 617 will be in this mode when it is first turned on. Pressing SHIFT/VOLTS will place

the instrument in the external feedback mode, as described in

paragraph 2.12.

OHMS--Pressing OHMS places the unit in the resistance measuring function. The indicator next to the OHMS button will be illuminated when the instrument is in this mode. Note

that there are two ways to measure resistance with the Model

617. Pressing OHMS alone will cause the instrument to measure resistance using the constant current method. Pressing the SHIFT button before pressing OHMS places the in-

2-2

strument in the V/I mode of resistance measurement, as

described in paragraph 2.8. The V/I indicator will light when the instrument is in this mode.

COUL-The Model 617 may be set up to measure charge by pressing the COUL button. The indicator next to the COUL button will illuminate when the instrument is set for this mode.

AMPS-Pressing AMPS switches the instrument to the current-measuring function. The AMPS indicator will turn on when the instrument is in this mode.

RANGE-These two buttons allow you to increment or decrement the range the instrument is in. Pressing the up ar- row button will move the instrument up one range each time it is operated, while the down arrow button will move the instrument down range one increment each time it is pressed.

Note that pressing either of these buttons will cancel autorange if that mode was previously selected. The display mantissa will remain blank until the first reading is ready to be displayed.

AUTO-The AUTO button places the instrument in the auto range mode. While in this mode, the Model 617 will switch to the best range to measure the applied signal. Note that the instrument will be in the autorange mode when it is first turned

on. Autoranging is available for all functions and ranges. Autoranging may be cancelled either by pressing the AUTO button or one of the two RANGE buttons.

ZERO CHECK-The zero check mode is used in conjunction with the ZERO CORRECT control to cancel any offsets within the instrument and is also used as a standby mode.

Pressing ZERO CHECK once will enable this mode, as shown by the associated indicator light. When zero check is enabled,

the electrometer input circuit configuration changes (see

paragraph 2.11). No readings can be be taken with zero check enabled. Pressing ZERO CHECK a second time will disable this mode. Zero check should be enabled when making connections or when changing functions.

ZERO CORRECT-The zero correct mode works with zero check to cancel electrometer offsets. If zero check is enabled, pressing ZERO CORRECT will store a new value that will be used to cancel any offset. If the range is changed while zero correct is enabled, the stored value will be scaled accordingly. Zero correct may be cancelled by pressing the ZERO CORRECT button a second time. More information on using zero correct may be found in paragraph 2.11.

may be disabled by pressing the SUPRESS button a second time, and is cancelled if the function is changed.

TRIG-The TRIG button allows you to enter the one-shot

trigger mode and trigger single readings from the front panel. To enter the one-shot mode, press SHIFT then TRIG. The SGL indicator light will show that the instrument is in the one-shot mode. Each time the TRIG button is pressed, a single reading will be processed and displayed. The displayed reading will flash when the TRIG button is pressed. The oneshot trigger mode can be cancelled by pressing SHIFT then TRIG a second time. Additional information on triggering may be found in paragraphs 2.13 and 3.10.14.

V-SOURCE-These buttons control the internal 2100V source within the instrument. More information on the using the voltage source is located in paragraph 2.8.

DISPLAY-The DISPLAY button toggles the front panel

display between the voltage source and the present display mode (electrometer or data store). Pressing DISPLAY once will switch the display from the present mode to the source

mode, as indicated by the LEDs adjacent to the display (more

information on the display is located in paragraph 2.4.2).

Pressing DISPLAY again will return the display to the

previous display mode.

ADJUST-These two buttons control the voltage source out-

put value. The up arrow button increases the voltage value in

50mV increments, while the down arrow decreases the

voltage source output in 5OmV increments. The values may

be scrolled by holding the desired ADJUST arrow in. The in-

strument will stop on the value currently displayed when the

button is released. The scrolling can be made more rapid by

pressing the SHIFT key before pressing the desire ADJUST

key. Note that the ADJUST keys are also used with certain

front panel programs, as described in paragraph 2.5. Note

that the maximum voltage values are +102.4V and

-102.35V.

OPERATE-The OPERATE button turns the actual voltage

source output on or off. Pressing the OPERATE button once

turns on the output. The LED next to the OPERATE button

will be illuminated when the source is turned on. Pressing the

OPERATE button a second time will turn off the output

(OO.oOV). Note that the OPERATE LED will flash when the

2mA current limit is exceeded.

SUPPRESS-The suppress mode allows you to cancel external offsets or store a baseline value to be subtracted from subsequent readings. For example, if you applied 1OV to the instrument and enabled suppress, that value would then be subtracted from subsequent readings. Once suppress is enabled, the value is scaled when the range is changed. Suppress

DATA STORE-The two DATA STORE buttons control the internal loo-reading data store mode of the instrument. Through these two buttons, data storage may be enabled or disabled, the storage rate may be selected, and readings may be recalled to the front panel display. Paragraph 2.12 con-

tains a complete description of data store operation.

2-3

ON/OFF--This control enables or disables data store opera-

tion. In addition, reading rates can be selected by holding the

button in when first enabling data store. When data store is enabled, the indicator light next to the ON/OFF button will be on. Minimum and maximum values are stored and up-

dated as long as the ON/OFF LED is on.

RECALL/EXIT-This single button serves to recall readings

previously stored by data store. Pressing and holding this

button causes the instrument to scroll through the pointer ad-

dresses as indicated on the display. Once the desired reading

number is displayed, releasing the button causes the actual

reading to be displayed. To exit the recall mode, press SHIFT

EXIT.

PROGRAM-A single PROGRAM button controls such

modes as IEEE address, alpha or numeric display exponent,

and digital calibration. Paragraph 2.5 further describes front panel programming.

SELECT/EXIT-This button enters the program mode to allow access to parameters described above. Pressing SELECT repeatedly causes the instrument to scroll through a program menu. To cancel the program mode, press SHIFT

and then SELECT/EXIT in that order. Note that the program mode is cancelled by pressing SELECT/EXIT after a program parameter change is made.

2.4.2 Display and Indicators

The operation of the 4% digit display and various indicators

is described below. The display updates at about three readings per second.

STATUS Indicators-These three indicators apply to operation of the Model 617 over the IEEE-488 bus. The REMOTE indicator shows when the instrument is in the IEEE-488 remote state, while the TALK and LISTEN indicators show

when the instrument is in the talk and listen states respect-

ively. See Section 3 for more information on using the Model 617 over the IEEE-486 bus.

2.4.3 Tilt Bail ’

The tilt bail, which is located on the bottom of the instru-

ment, allows the front panel to be elevated to a convenient viewing height. To extend the bail, rotate it out 90” from the bottom cover and latch it into place. To retract the bail, pull

out until it unlatches and rotate it against the bottom cover.

2.5 FRONT PANEL PROGRAMS

The Model 617 has three front panel programs that can be used to set the primary address, set the display exponent mode (alpha or numeric), or calibrate the instrument from the front panel. To select a program, press PROGRAM SELECT button repeatedly while bbserving the display. The instrument will scroll through the available programs with identifying messages. as shown in Table 2-2. When in the program

mode, the DISPLAY and DATA STORE RECALL buttons are inoperative; the data store mode may be turned off, but not on. The operation of the various programs is described in

the following paragraphs. To exit a program, press SHIFT EXIT. If a change was made, pressing SELECT alone will exit

the program.

Display-The Model 617 has a display made up of a 4% digit

signed mantissa as well as a two-digit signed exponent. The exponent can be represented either in scientific notation, or with an alphanumeric subsript such as nA. The exponent dis-

play mode can be changed with a front panel program, as

described in paragraph 2.5. Note that, when scientific nota-

tion is used, the decimal point remains fixed as in 1.9999. The

range is indicated by the exponent. In addition, the display

has a number of front panel error messages, as shown in

Table 2-l.

Display Indicators-The METER, SOURCE, and DATA LEDs indicate what the display is actually showing. When the METER LED is on, the display represents an electrometer reading. When the SOURCE LED is illuminated, the voltage source value is being displayed. A data store reading is displayed when the DATA LED is turned on. Normally, the display will be the the meter mode, but the DISPLAY and RECALL buttons will switch the display to the source and data modes respectively.

2-4

2.5.1 IEEE-488 Address

Selection of the IEEE-488 address program is indicated by the following message:

IEEE 27

Along with the message, the presently programmed IEEE-488 address (27 in this example) will be displayed. To select a new address, use the V-SOURCE ADJUST keys. When the desired value is shown in the display, press SHIFT then SELECT EXIT to return to normal operation (or if a change was made, simply press SELECT). For complete information on using the

Model 617 over the IEEE-488 bus, refer to Section 3.

Table 2-1. Display Error Messages

Message

b Err

Description

Overrange input applied (- for negative valueI.

Bus Error: Instrument programmed while npt in remote; ~ or illegal command or command option sent.*

n Err

(Number Error: Calibration or voltage source value out of ; limits.*

‘t Err

Trigger Overrun Error: Instrument triggered while processing reading from previous trigger.

“See Section 3.

Table 2-2. Front Panel Program Messages

Displays/sets IEEE primary address.

IdlSP

Sets numeric or alpha exponent.

The display in the alpha mode appears as:

dISI’m

Once the desired exponent mode is selected, press SHIFT then SELECT EXIT to return to normal operation (or simply PRO- GRAM SELECT if a change was made).

2.5.3 Calibration

CAL

Allows calibration of instrument.

2.5.2 Exponent Mode (Alpha or Numeric)

The display exponent of the Model 617 can be operated in either the alpha mode or the numeric mode. In the alpha

mode, the exponent is given in actual units such as mA. In the numeric mode, the exponent is given in scientific notation.

Table 2-3 gives typical examples. including units.

To select the exponent program, scroll through the program

menu until the following message is displayed:

dISI’

Use either of the V-SOURCE ADJUST buttons to set the ex- ponent to the desired mode. In the numeric mode, the display might show:

dISP -3

An advanced feature of the Model 617 is its digital calibration

program. The instrument can be calibrated from the front panel or over the IEEE-488 bus. To use the front panel calibration program, refer to the calibration procedures outiined in Section 7.

2.6 REAR PANEL FAMILIARIZATION

The rear panel of the Model 617 is shown in Figure 2-2.

2.6.1 Connectors and Terminals

AC Receptacle-Power is applied through the suppiied power cord to the AC receptacle. Note that the supply voltage is marked adjacent to the receptacle.

IEEE-488 Connector-This connector is used to connect the

instrument to the IEEE-488 bus. IEEE-488 function codes are

marked above the connector.

2-5

Table 2-3. Typical Display Exponent Values

I Display

IPA

Tfl

ingineering

Units

!lC

kCI

icientific Uotation

10-77-A

10-w

lo-GA

lo-3v

103Q

lO@l

low

1012sl

anocoulombr

licroamperes

Millivolts

Kilohms

Megohms

Gigohms

Teraohms

INPUT-The INPUT connector is a 2-lug triax connector to be used for all electrometer signal inputs. Note that you should not confuse a triaxial connector with the BNC type that is used for the EXTERNAL TRIGGER and ELEC-

TROMETER COMPLETE connections. Also, do not attempt

to force a 3-lug triaxial connector onto the INPUT Connector. The Models 6171 and 6172 adapters are available to make the necessary conversion.

2V ANALOG OUTPUT-The 2V ANALOG OUTPUT prc-

vides a scaled O-2V output from the electrometer (2V output

for full range input). The output uses a standard S-way bind-

ing post and is inverting in the volts and ohms modes.

PR!ZAMP OUT-The PREAMI’ OUT provides a guard cutput for voltage and resistance measurements. This output can also be used as an inverting output or with external feedback when measuring current or charge. The PREAMP OUT has a maximum output value of k3C0V and uses a standard s-way binding post.

WARNING Hazardous voltage may be present at the PREAMP OUT, depending on the input

signal.

101522

COM Terminal-The COM terminal is a 5way binding post that provides a low connection for both the 2V ANALOG OIJ’IT’LT and the PREAMP OUT This terminal is also used for input low connection when in guarded mode; COM is internally connected to input low through a lC0Q resistor. Do not connect PREAMP OUT, COM, or 2V ANALOG OUTPUT to earth when floating input.

V-SOURCE OUTPUT-The HI and LO outputs are the connections for the internal voltage source. This source can be used as a stand-alone source or in conjunction with the elec-

trometer section to make resistance measurements as high as

1owL

EXTERNAL TRIGGER INPUT-This BNC connector can be used to apply external trigger pulses to the Model 617 to trigger the instrument to take one or more readings, depending

on the selected trigger mode.

Petaohms

2-6

Figure 2-2. Model 617 Rear Panel

METER COMPLETE OUTPUT-This BNC connector prcvides an output pulse when the Model 617 has completed a reading; it is useful for triggeling other instrumentation.

Chassis Ground-This jack is a s-way biding post that is connected to instrument chassis ground. It is intended for use in situations requiring an accessible chassis ground terminal.

A shorting link is supplied and connected to the CHASSIS GROUND terminal.

2.6.2 V, !I GUARD Switch

The Model 617 has provisions for connecting a guard to the

inner shield of the input cable. Guarding is useful in the volts and ohms modes to speed up response time and minimize the effects of leakage resistance. Note that guarded operation is not recommended in amps or coulombs. The V, Q GUARD switch allows easy selection of the guarded mode of cperaticn. See paragraph 2.7.4 for more information on guarded operation.

2.6.3 Line Fuse

The LINE FUSE, which is accessible on the rear panel, pro

vides protection for the AC power line output. For infcrmaticn on replacing this fuse, refer to Section 7.

2.7 BASIC MEASUREMENT TECHNIQUES

The paragraphs below describe the basic procedures for using

the Model 617 to make voltage, resistance, charge, and current measurements.

2.7.1 Warm Up Period

The Model 617 is usable immediately when it is first turned on. However, the instrument must be allowed to warm up for at least two hours to achieve rated accuracy.

NOTE

While rated accuracy is achieved after the two hour wan-n up period, input bias current may require additional time to come to its optimum level. Allow two hours for input bias current to settle to less than 1OfA and eight hours to less than 5fA. It is preferable in sensitive applications to leave the unit on continuously.

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2.7.2 Input Connections

The rear panel IivPIJT connector is a Teflon-insulated receptacle intended for all input signals to the Model 617. As shown in Figure 2-3, the center terminal is high, the inner ring or shield is low, and the outer shield is connected to instrument chassis ground. In the guarded mode, the inner shield is driven at guard potential, while the Outer shield is chassis ground.

NOTE

The input connector must be kept clean to main-

tain high input impedance.

The supplied Model 6011 input cable is designed to mate with the input connector. The other end of the Model 6011 is terminated with three alligator clips. Input high is color coded in red, input low is colored black, and chassis ground is color coded in green. Keep in mind that these connections are for

the unguarded mode. In the guarded mode, red is high, black is guard, and green is chassis ground. The COM binding post

provides a connection to input low through loOn for use in

the guarded mode.

GROUND

CAUTION

The maximum voltage between input high

and input low is ZXlV rms. DC to 60Hz sine wsve (10 seconds maximum in mA ranges). Exceeding this value may cause damage to

the instrument.

2.7.3 Making Voltage Measurements

The Model 617 can be used to measure voltages in the range of *lOpV to +2COV. In principle, the instrument operates much like an ordinary DMM, but its special characteristics allow it to make measurements in cases where an ordinary DMM would be unable to perform well. In particular, the very high input resistance of 2oOTSl (2 X 1OW) allows it to accurately measure voltage sources with high internal resistances. In contrast, an ordinary DMh4 may have an input resistance of only loMa. resulting in inaccurate measurements because of instrument loading.

Use the procedure below to make voltage measurements.

1. Turn on instrument power and allow it to warm up for two hours to reach rated accuracy.

2. Check to see that the voltage function is selected by pressing the VOLTS button. Use the autorange mode, or select the desired range with the ranging pushbuttons.

3. To achieve specified accuracy, especially on the lower ranges, it is recommended that you zero the instrument. To do so, first enable zero check and then press the ZERO CORRECT button. Correcting zero in the lowest range of any function will correct all ranges because of internal scaling.

A. UNGUARDED 6. GUARDED

I”, ii GUARD OFF)

Figure 2-3. Input Connector Configuration

NOTE

W, R GUARD ON,

It is recommended that zero check be enabled when connecting or disconnecting input signals.

WARNING The maximum common-mode input voltage (the voltage between input low and chassis ground1 is 5OOV peak. Exceeding this value may create a shock hazard.

CAUTION

Connecting PREAMP OUT, COM, or 2V ANALOG

XJTPUT to earth while floating input may

damage the instrument.

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NOTE

The input circuit configuration changes with zero check enabled. See paragraph 2.11.1.

4. Connect the Model 6011 triaxial input cable or other similar cable to the rear panel INPUT jack on the instrument. For sources with high output resistance, the cable should be kept as short as possible to minimize cable capacitance.

5. If response time and leakage resistance are considerations, place the instrument in the guarded mode as described in the next paragraph.

6. Connect the other end of the cable to the voltage to be

measured, as shown in Figure 2-4. Disable zero check.

7. The reading may be obtained directly from the display.

The exponent can be placed either in the alpha or numeric

mode, as described in paragraph 2.5.

I+ I

vs= j

T- I

Figure 2-4. Connections for Voltage Measurements

TO A/D CONVERTER

Voltage Measurement Considerations: Two primary considerations come to mind when making voltage measurements. especially for voltage sources with high output resistances. For one thing, the loading effects of the measuring instrument come into play at the high resistance levels involved. Secondly, the distributed capacitance of the source, the input cable, and the input circuit of the instrument itself come into play when making these measurements.

To see how meter loading can affect accuracy, refer to Figure 2-5. In this figure there is a voltage source with a value ES and

an output RS connected to the input of the electrometer, which has its input resistance represented by RIN. The percent error due to loading can be calculated as follows:

100 RS

% ERROR = -

Rs + RIN

Thus, to keep the error under 0.1%. the input resistance must be about 1000 times the value of the source resistance. R.

At very high resistance levels, the very large time contants created by even a minimal amount of capacitance can slow

down response time considerably. For example, measuring a wurce with an internal resistance of 1OOGQ would result in an

RC time constant of one second when measured through a cable with a nominal capacitance of 1OpF. If 1% accuracy is required, a single measurement would require at least five seconds.

Basically, there are two ways to minimize this problem: (1)

keep the input cable as short as possible, and (2) use guarding.

With the first method, there is a limit as to how short the

cable can be. Using guarding can reduce these effects by up to

a factor of 1000. The Model 617 has a rear panel switch to

allow guarding to be easily applied to the input circuit: see the

next paragraph for details.

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At low signal levels, noise may affect accuracy. Shielding of the unknown voltage can reduce noise effects substantially. When using shielding, the shield should be connected to input IOW.

rI /

To approach the concept of guarding, let us first review the

unguarded circuit shown in Figure 2-6. The measured signal is represented by the voltage source ES and the source resistance

RS. Cable leakage impedance is represented by 2~ The

source resistance and leakage impedance form a voltage

divider that attenuates the source voltage as follows:

ZLES

E, =

ZL + Rs

Thus, to keep the error due to leakage resistance under O.l%,

the leakage resistance must be at least 1000 times the source resistance value.

T ; / N”!

---- J

G-lJ

L-----J

Figure 2-5. Meter Loading Considerations

2.7.4 Guarded Operation

Guarding consists of using a conductor supplied by a low impedance source to totally surround the leads carrying a highimpedance signal. The output of this low-impedance source is kept at the same potential as the signal itself, resulting in drastically reduced leakage currents.

Guarding the circuit miminizes these effects by driving the

shield at signal potential, as shown in Figure 2-7. Here, a uni-

ty gain amplifier with a high input impedance and low output impedance is used. The input of the amplifier is connected to the signal, while the output is used to drive the shield. Since

the amplifier has unity gain, the potential across ZLis essentially zero, so no leakage current flows. Leakage between

the cable shield and ground may be considerable, but it is of no consequence since that current is supplied by the low impedance source, rather than by the signal itself.

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Figure 2-6. Unguarded Circuit

Figure 2-7. Guarded Circuit

-I

low input offset current. The low voltage burden is achieved because the Model 617 measures current as a feedback type picoammeter, rather than the shunt method used by many DMMs.

NOTE

After measuring high voltage in volts, or following an overload condition in ohms, it may take a number of miriutes for input current to drop to within specified limits. Input current can be verified by placing the protection cap on the INPUT jack and then connecting a jumper between the COM and chassis ground terminals, With the instrument on the 2pA range and zero check disabled, allow the reading to settle until the instrument is within specifications.

NOTE

Safe operation and good measurement practice dictates the use of an external resistor when necessary to limit currents to less than 3011~4.

When the rear panel V, Q GUARD switch is placed in the ON position, guard potential is placed on the inner shield of the

triaxial cable. The other shield remains at chassis ground. Thus, it is necessary to use the COM terminal for low signal connections, as shown in Figure 2-0. For very critical measurements, a shielded, guarded enclosure should be used.

WARNING

Hazardous voltage lup to 3OOV) may be present on the inner shield when V, Q GUARD is on, depending on the input signal. A safety shield, connected to chassis ground is

recommended when making voltage

measurements over 30V or guarded resistance measurements.

NOTE

The use of guarding is not recommended in amps or coulombs.

The PREAMI’ OLJT terminal may be used for guarding in the volts and ohms modes in a similar manner. In this mode, the

preamplifier acts as a unity gain amplifier with low output impedance.

WARNING Hazardous voltage (up to 3WV) may be present at the PREAMP OUT terminal, depending on the input signal.

2.7.5 Making Current Measurements

The Model 617 can resolve currents as low as 0.1 fA

(lo--lbA), and measure as high as 2011~4 in 11 ranges. The

Model 617 exhibits low input voltage burden and extremely

To measure current with the Model 617, use the following procedure.

I. Turn on the power and allow the instrument to warm up

for at least two hours to obtain rated accuracy.

2. Select the current mode by pressing the AMPS button on

the front panel. Set V, Q GUARD to OFF.

3. To achieve rated accuracy, select the 2pA range, zero the instrument by enabling zero check and then pressing the ZERO CORRECT button. Select the desired range, or use

autoranging if desired.

4. Connect the Model 6011 or other similar cable to the rear

panel INPUT jack. Connect the other end of the circuit to be measured as shown in Figure 2-9. Shielding will be required for low-level measurements. Connect the shield to input low.

5. Disable zero check.

6. Read the current value directly from the display. The exponent may be placed either in the alpha or numeric modes, as described in paragraph 2.5.

Current Measurement Considerations: At very low levels (in the picoampere range), noise currents generated in the cable or from other sources can affect measurements. Currents generated by triboelectric effects are a primary cause of noise currents generated in connecting cables. These currents are generated by charges created at the junction between a conductor and an insulator because of friction. Coaxial and triaxial cables are especially prone to such noise currents, which are generated by cable flexing. To minimize these effects, the cable should be tied down firmly to minimize any flexing. Also, special low-noise cable, constructed with graphite be-

tween the shield and insulator, is available to minimize these

effects. However, even with low-noise cables, several tens of

femtoamps of noise currents can be generated by cable move-

ment.

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