Keithley 602 Service manual

MODEL 602 INSTRUCTION MANUAL

Instruction Manual

Solid-State Electrometer

Model 602

Publication Date: June 1963 Document Number: 29111 Rev. C

Contains Operating and Servicing Information for the

Model 602 Solid-State Electrometer

01975, Keithley Instruments, Inc.

Cleveland, Ohio, U.S.A.

Document Number 29111

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 we 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 pmduct modification without Keithley’s express written consent, or misuse of

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

problems arising from normal wear or failure to follow instructions.

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

NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND

SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS OF REMOVAL

AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.

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

SPECIFICATIONS

AS A VOLTMETER: RANGE: .OOlV full scale to 1OV in nine’lX and 3X ranges. ACCURACY: f 1% of full scale on all ranges exclusive of noise and drii. ZERO DRIFT: Less than Im” per 24 hours, Ikss than 150@ per OC. METER NOISE: *25&J maxim”m with input shoned on most sensitive

IN?~?iMPEDANCE: Greater than lo’% shunted by2OpF. Input resistance AS iN AMMETER:

RANGE: lCr14A full scale to 0.3A in twenty-eight 1X and 3X ranges. ACCURACY: 12% of full scale on 0.3 to 10”A ranges using the mallest

available multiplier setting; *t4% of full scale on 3 x lo-l2 fo 10-14A

ranoes. METER NOISE: Less than f3 x 10-16A. OFFSET CVRRENT: Lens than 5 x 10-15A.

AS AN OHMMETER: RANQE: 7000, full scale to 10% in twent+hree linear IX and 3X ranges. ACCURACY: *3% of full scale on 100 to l@Q ranges using the largest

available multiplier stting; f5% of full scale on 3 x 109 to 1O’jn ranges. AS AN COULOMBMETER:

RANGE: lo-‘? full scale to 10dC in fifteen IX and 3X ranges. ACCURACY: f5% of full scale on all ranges. Dritt due fo offset current

does no, exceed 5 x 10.=C per second. AS AN AMPLIFIER:

tNPUT IMPEDANCE: Greater than 10’40 shunted by2OpF. input resistance

may a,so be ~&cted in decade steps from 10 fo lO”O. OUTPUTS: Unitygain output and either voltage or cment recorder o”tp”t. UNITY-QAIN OUTPUT: At DC, o”tp”t is equal to input within 10 ppm. ex-

clusive of noise and drib?. for o”tp”t currents of lOO@ or less. Up 10 ImA

may be drawn for input voltages of 10” or less. Output polarity is same as input p&dry.

VOLTAGE RECORDER OUTPUT: *lV for full-scale input. Internal

resistance is g1M1. Output polarity is opposite input polarity. Gain: 0.1. 0.33, a.. to 1000. Frequmw Response lwithin 3db): DC to 40kHr 81 a gain of 1 and

lo&, &e&g to DC to 1OOHz at maximum gain. Full o”tp”t response limited to 3kHz on any gain.

Noise: Less than 3% ms of full scale at gain of 1000. decreasing 10 less

than 0.5% ar gains below 10.

CURRENT RECORDER OUTPUT: i ImA for full-scale input. variable

f6% wtih 14OOll recorders.

GENERAL ISOLATION: Circuit ground to chassis ground: Greater than l@Q shunted

by .0016~F. Circuit ground may be floated up to f 15OOV with wpecf to chassis ground.

Polarity: Meter *witch seIects lefvzero Ipositive or negative) or center-zero

scales. Meter witch does nof reverse polarity of o”fp”tS.

CONNECTORS: Input: Teflon-insulated tdaxial Bendix 33050-Z. Low:

Binding post. Voltage or currem o”tp”t: Amphenol 60.PCZF. Unity-gain

o”tp”1, chassis ground: Binding posts.

BATTERY CHECK: Condition of all baneries may be checked with front

paw co”trok.

BATTERIES: Six 2N6 lor 246. VS306. NEDA 16021: one RM-1W. 1000 DIMENSIONS. WEIGHT: Overall bench size 10% in. high x 7 in. wide x

11 ‘h in. deep 1276 x 175 x 2gOmm). Net weight. 13 pounds l57kgl.

ACCESSORIES SUPPLIED: Model 6011 Input Cable: 30” triaxial cable

with friaxial connector and 3 alligator clips. Mating o”tp”f connector.

TABLE OF CONTENTS

Paragraph

SECTION l-GENERAL DESCRIPTION

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.8.1

1.82

1.8.3

1.8.4

1.8.5

1.8.6

1.8.7

2.1

2.2

2.3

2.4

2.5

2.6

2.6.1

2.6.2

2.6.3

2.7

2.7.1

2.7.2

2.8

2.8.1

2.6.2

2.8.3

2.9

2.9.1

2.9.2

2.9.3

2.10

2.11

2.12

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

Model 602 Features. ....................

Warranty Information ...................

ManualAddenda

Safety Symbols and Terms. ..............

Safety Precautions

Specifications .........................

Optional Accessories. ...................

SECTION Z-OPERATION

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

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

Rear Panel Terminals. ..................

Input Connections .....................

Preliminary Procedures. ................

Voltage Measurements. ................

Off-Ground Voltage Measurements .......

Current Measurements .................

Resistance Measurements ..............

Charge Measurements .................

Recorder Outputs .....................

Unity-Gain Output .....................

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

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

Model 6101A Shielded Probe ...........

Model 6103C Divider Probe

Model 6104Test Shield. ...............

Model 6105 Resistivity Chamber ........

Model 2503 Static Detector Probe.

Model 6011 Input Cable ...............

Model 6012 Triax-to-Coax Adapter ......

Normal Method Voltage Measurements Guard Method Voltage Measurements

Low Impedance Source ..............

FEEDBACK Switch Set To NORMAL ...

FEEDBACK Switch Set To FAST ......

Normal Mode IO.3 to lO~‘4A Ranges) ....

Fast Method (Current Below lo-=A) ....

Galvanometric Method ...............

Normal Constant Current Method ......

Fast Constant Current Method. ........

Voltmeter-Ammeter Method (To 10%)

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

......

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

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

Title Page

.........

...... ..

.........

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

2-1 2-l 2-l 2-l 2-4 2-5 2-5 2-5 2-5 2-5 2-5 2-5 2-6

2-6 2-6 2-7 2-7 2-7 2-8 2-8 2-8 2-9 2-9

......

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

......

3.1

3.2

3.3

3.4

3.4.1

3.4.2

3.5

3.5.1

3.5.2

3.6

SECTION 3-THEORY OF OPERATION

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

Voltmeter Operation ...................

Voltmeter Circuit ......................

Ammeter Operation. ...................

Normal Method .....................

Fast Method. .......................

Ohmmeter Operation ..................

Normal Method .....................

Guarded Method ....................

Coulombmeter Opration ................

......

,,....

......

.,....

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

......

3-l

3-1

3-l 3-1 3-l

3-2 3-2

3-2

4.1

4.2

4.2.1

4.2.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10

4.10.1

4.10.2

4.10.3

4.10.4

4.11

4.12

4.13

4.14

4.14.1

4.14.2

4.15

4.16

SECTION 4--SERVICING INFORMATION

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

Calibration

RecommendedEquipment

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

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

CalibrationSchedule ..........................................................................

Preliminary Procedures Mechanical Meter Set and Meter Zero Calibration

Tracking Check and 1MA Output Calibration

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

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

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

NoiseCheck ...................................................................................

OffsetCurrentCheck DrinCheck

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

High-Megohm ResistorVerification. AccuracyCheck

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

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

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

VoltageAccuracyCheck .......................................................................

CurrentAccuracyCheck .......................................................................

ResistanceAccuracyCheck

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

ChargeAccuracyCheck .......................................................................

Unity-GainCheck

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

FrequencyResponseCheck ......................................................................

CommonModeRejectionCheck ..................................................................

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

Servicing Schedule ...........................................................................

Par&Replacement Procedures To Guide Troubleshooting Servicing High Impedance Circuitry

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

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

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

41 4-l 4-l 4-l 4-l 4-2 4-2 4-2

z 4-3 4-3 43

2

4-4 zl

4.4 45

z

4.2 4-6

5.1

5.2

5.3

5.4

5.5

5.6

5.7

SECTION S-REPLACEABLE PARTS

Introduction

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

PartsList .....................................................................................

OrderingInformation ............................................................................

FactoryService ................................................................................

Special Handling of Static Sensitive Devices ComponentLocationDrawing

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

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

SchematicDiagram.........................,.,.............,,..,............................... o-1

5-l 5-l 51 5-l 51 51

r*

ii

LIST OF FIGURES

Figure

Model 602 Front Panel Controls

2-1

Model 602 Rear Panel Terminals

2-2

Triaxiallnput ..........................................................

2-3

Error Due to Ammeter Resistance.

2-4

Measuring Current by the Galvanometric Method,

2-5

Measuring Resistance by the External Voltage Method

2-6 2-7 Divider Curcuits ccross Model 602 Output for Driving 50 and 10OmV Recorders

Measuring Potential of Hich Resistance Source with 0.025% Accuracy.

2-8

Block Diagram of Model 602 in Voltmeter Mode

3-1

Block Diagram of Model 602as a Picoammeter

3-2

Block Diagram of Model 602for Normal Method Measuring Resistance

3-3 4-l Model 602 Case to LO Isolation Check

Model 602 Unity-Gain Test Set-Up.

4-2

Model 602 Chassis, Side View.

5-1

RANGE Switch, S102, Component Location Drawing

5-2

MULTIPLIER Switch, S106, Component Location Drawing

5-3

Model 602, PC186, Component Location Drawing

5-4

Model 602, PC127, Component Location Drawing

5-5

Model 602, Schematic Diagram, Dwg. No. 21174E

5-6

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

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

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

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

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

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

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

Title

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

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

.........

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

.........

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

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

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

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

LIST OF TABLES

...

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

Page

.........

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

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

......... 2-6

......... 2-7

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

......... 2-9

.........

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

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

......... 4-4

.........

......... 53

.........

......... 5-9

2-2

3-l

5-2

57 5-7

Table 2-l Color Coding of Alligator Clips for Model 6011 Input Cable ... 2-2 Multiplier Switch Positions for Checking

4-1 Recommended Test Equipment .........................

4-2 Model 602 Internal Controls. 4-3 Coulomb Ranges Accuracy Check 4-4 Model 602 Troubleshooting. 5-l Model 602 Static Sensitive Devices 5-2 Model 602 Replaceable Parts List

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

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

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

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

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

Title

......

..,...

Page

2-l 2-4 4-l

4-2 4-4 4-5 5-l 54

iii/iv

SECTION 1

GENERAL DESCRIPTION

1.1 INTRODUCTION 1.3 WARRANTY INFORMATION The Keithley Model 602 Electrometer is a completely solid-

state, battery operated instrument, which measures a wide

range of DC voltage, current, resistance and charge. The Model 602’s input resistance of greater than 10’4R is the result of extensive instrument development with high input impedance transistors. The Model 602 has all the capabilities of conventional VTVMs, but can also make more measure-

ments without loading circuits.

The Model 602 has nine voltage ranges from O.OOlV full scale to lOV, 28 current ranges from 10’4A full scale to 0.3A. 23

linear resistance ranges from 1000 full scale to 1OtQ. and 15

charge ranges from lo-‘SC full scale to lo-aC. The Model 602 offers complete line isolation and excellent

off-ground measuring capability. Up to 1500V may be applied instrument which occur after the printins o! this manual will

between the input low terminal and the case, and stage be found on an addendum sheet included .-:ith this manual.

operation is assured with the case grounded. A triaxial con- Be sure to review these changes before ar:en:$ing to operate

nectar allows complete guarding of the high impedance input or service the instrument. terminal.

The Model 602 employs matched insulated-gate field-effect

transistors followed by transistor differential amplifier stages

and a compliritentary-output stage. A large amount of

negative feedback is used for stability and accuracy.

1.2 MODEL 602 FEATURES

1. The Model 602 has excellent zero stability which permits accurate measurements with minimal adjustment. Short term zero drift is less than 50& per hour. Zero offset due to temperature change is less than 15O/rV per OC after 30 minute warm-up period. This offset, however, can easily be compensated for with the front panel zero controls.

2. Fast warm-up is an inherent characteristic of the Model

602. It can be operated 30 minutes after warm-up on the

most sensitive range and almost immediately on less sensi-

tive ranaes.

3. Low offset current 5 X lo-IsA, minimizes zero offset with high source resistance and permits maximum resolution

when measuring current and charge.

4. The 1000 hour life of the batteries enables usage in long term experiments without interruptions for recharging.

Battery life is maintained even when the 1OmA recorder output is used. For further convenience, battery condition is readily checked on the panel meter.

5. Excellent overload protection without degradation of performance is obtained by use of a unique input circuit. The

Model 602 Electrometer will withstand damage and has good recovery.

Warranty information may be found inside the front cover of this manual. Should it become necessary to exercise the warranty, contact your nearest Keithley representative or the factory to determine the correct course of action. Keithley

Instruments maintains service facilities in the United States,

West Germany, Great Britain, France, the Netherlands,

Switzerland, and Austria. Information concerning the appli-

cation, operation, or service of your instrument may be directed to the applications engineer at any of these locations. Check the inside front cover of this manual for addresses.

1.4 MANUAL ADDENDA

Information concerning improvements or changes to the

1.5 SAFETY SYMBOLS AND TERMS

The following safety symbols and terms are used in this

manual or found on the Model 602.

The symbol

should refer to the operating instructions in this ;nanual.

The symbol

tential of 1OOOV or more may be present on the terminaltsl.

Standard safety precautions should be observed when such dangerous voltages are encountered.

The WARNING heading in this manual explains dangers that could result in personal injury or death.

The CAUTION heading in this manual explains hazards that could damage the instrument.

1.6 SAFETY PRECAUTIONS

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

2. Excercise extreme caution when a shock hazard is present at the instrument’s input. The American National

Standards Institute (ANSI) states that a shock hazard ex-

ists when voltage levels greater than 30V rms or 42.4V

peak are present. A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring.

on the instrument indicates that the user

A

#

on the instrument indicates that a po-

l-l

3. 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.

4. 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.

5. 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.

6. Exercise extreme safety when testing high energy power circuits (AC line or mains, etc). Refer to the operating section.

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

1.7 SPECIFICATIONS

Detailed Model 602 specifications may be found immediately preceding this section.

Three-Terminal Connections-The GUARD output on the Model 602 Electrometer can be used for resistance measurements where the effects of cable capacitance may be significant. Connect the unknown between INPUT and EXT terminals. Connect the EXT terminal to the GUARD output on the electrometer. Use the electrometer in fast mode for ohms measurement.

I.E.4 Model 6105 Resistivity Chamber

The Model 6105 is a guarded test fixture for measurement of surface and volume resistivities. The chamber is designed in accordance with ASTM Standard Method of Test for Electrical Resistance of Insulated Materials, D257-66. The Model 6105 can be used in conjunction with an electrometer and voltage supply.

Resistivity can be determined by measuring the current through a sample with a known voltage impressed. The measurement can be made most conveniently when a set of

electrodes are used which can be calibrated in terms of surface or volume resistivity. The Model 6105 has been designed for use with a Keithley electrometer and an optional high voltage supply such as the Model 247.

1.8 OPTIONAL ACCESSORIES

The following optional accessories can be used with the

Model 602 to provide additional convenience and versatility.

1.8.1 Model 8lOlA Shielded Probe The Model 6010A is a shielded cable with a needle point

probe and 30 inches of low noise cable terminated by a UHF connector.

I.E.2 Model 8103C Divider Probe The Model 6013C is a shielded cable with a needle point

probe and 30 inches of low noise cable terminated by a UHF connector. The probe includes a 1OOO:l voltage divider with a

4.5 X 1OW input resistance. Accuracy is f5% at 30kV.

1.8.3 Model 8104 Test Shield

The Model 6104 is a shielded test box for two-terminal or three-terminal connections. The INPUT terminal is Teflon@ insulated.

Two-Terminal Connections-Resistance measurements can be made conveniently using the INPUT and GROUND terminals on the test box. Connect the electrometer to the BNC output. Use the electrometer in normal mode for ohms measurement.

1.8.5 Model 2503 Static Detector Probe Model 2503 is designed to detect voltage due to charge on

relatively small surface areas. Solid coaxial 13mm (% inch) diameter tube used with 89mm (3% inch) head, 89mm (3% inch) coupler, 25mm (one inch) adapter and two 90° angle adapters which may be placed at various junctions along the tube. It gives a 10,OOO:l & 10% divsion ratio when used with Model 610C and held 6mm (‘/ inch) away from a charged plane of at least 13mm (% inch) diameter. Output is a UHF male plug.

I.E.8 Model 8011 Input Cable The Model 6011 is a low-noise triaxial cable, 30 inches long,

terminated by three color-coded alligator clips. This cable mates directly with the triaxial input. The cable is fabricated using a Keithley connector (P/N CS-141) and low-noise cable (P/N SC-22).

The Model 6011 may be used for measurements which require a triaxial connection, especially when the input LO is floated above CASE ground.

I.E.7 Model 6012 Triax-to-Coax Adapter The Model 6012 is an adapter for mating the triaxial input and

UHF (coax) type connectors. Permits using Models 220,602, 614, 616 and 619 with all Keithley electromete accessories having UHF type connectors.

l-2

2.1 INTRODUCTION

SECTION 2

OPERATION

connected to case ground, only if the shorting link on the rear panel is connected.

A layout of the Model 602 front panel controls is contained in

Figure 2-1, while Figure 2-2 contains a layout of the rear panel terminals. See the following paragraphs for Model 602 front panel controls and rear panel terminals.

2.2 FRONT PANEL CONTROLS

Range Switch-Selects the mode to be measured: voltage, current, resistance or charge.

Multiplier Switch-Determines full scale voltage sensitivity and can be used to multiply current, resistance and charge ranges on the range switch.

METER Switch-Checks battery condition, turns instrument off, disconnects meter, selects meter polarity, sets instrument for center zero operation.

ZERO Control-Allows precise meter zeroing. ZERO CHECK Switch-Zeroes meter on any range.

FEEDBACK Switch-Determines the feedback connections within the instrument.

INPUT Connector-Connects input to source. Connector is a Teflon” insulated triaxial connector.

LO Terminal-Provides connection to input low.

2.3 REAR PANEL TERMINALS COARSE ZERO Switch-Extends the zeroing capability of

the front panel ZERO controls. lMA/IV Switch-Selects the Model 602 output: 1mA or

1V. Must be in 1V position if the output is connected to a load of more than 2kQ.

IMA CAL Control-Varies the output from 0.95 to 1.05mA.

OUTPUT Connector-Connects output to monitoring

device.

Xl OUTPUT and OHMS-GUARD Terminals-For guard-

ed measurements and for use as an extremely linear

preamplifier.

LO Terminal-Provides an alternate connection to input

low.

CASE GND Terminals-Connects to Model 602 cabinet and outside shell of input connector.

2.4 INPUT CONNECTIONS The Model 602 INPUT connector is a TeflonO insulated

triaxial connector. The center terminal is a high impedance terminal, the inner shield is a low impedance terminal and the outer shield is case ground (See Figure 2-3). The LO terminal, below the connector, is connected to the inner shield. It is

The Model 6011 Input Cable is supplied with the instrument, Table 2-1 indicates the color coding of the alligator clips. The high impedance terminal is shielded by the inner braid of the triaxial cable up to the miniature alligator clip. If the unshielded clip causes pick-up from nearby electric fields, remove the clip, and connect the shielded lead directly to the source.

Table 2-l. Color Coding of Alligator Clips For Modal

8011 Input Cable

Lead Heavy wire with

red clip cover.

Thin wire with black clip cover.

Thin wire with green clip cover.

When working with a high impedance source carefully shield the input connection and the source since any variation in the electrostatic field near the input will cause definite meter disturbances.

Use high resistance, low loss material (such as, Teflon@ , polyethylene of polystyrene) for insulation. The insulation

leakage resistance of test fixtures and leads should be several orders of magnitude higher than the internal resistance of the source. Excessive leakage reduces the accuracy of reading

from high impedance sources. The triaxial or coaxial cables

used should be a low noise type which employs a graphite or

other conductive coating between the dielectric and the sur-

rounding shield braid. The Model 6011 input cable ensures

good input connections. When working with a high impedance source, any change in

the shunt capacitance of the input circuit will cause disturbances in the reading. Make the measuring setup as rigid as possible, tie down connecting cables to prevent vibrations.

A continuous vibration may appear at the output as a

sinusoidal signal, and other precautions may be necessary to

isolate the instrument and connecting cable from the vibra-

tions.

Clean, dry connections and cables are very important to maintain the value of all insulation materials. Even the best insulation will be com-

promised by dust, dirt, solder flux, films, oil or water vapor. A good cleaning agent is methyl alcohol, which dissolves most common dirt without chemically attacking the insulation. Air dry the cables or connections after washing with alcohol or use dn/ nitrogen or Freon.

Circuit

Input High Center

Input Low

Case Outer Shield

NOTE

JIOI Terminal

Inner

2-1

2-2

Figure 2-l. Model 602 Front Panel Controls