Keithley 197 Service manual

Instruction Manual

Model

197

Autoranging Microvolt

DMM

0

Keit hley Instruments, Inc.

Cleveland,

Document Number 197-901-01

Ohio,

U.S.A.

DC

VOLTS

RANGE LUTION RESISTANCE 22'-24"C 18"-28'C

-

200mV

2V

20

200

loo0

*Relative to calibration accuracy.

NMRR:

Greater than 6OdB at

MAXIMUM ALLOWABLE INPUT:

minute on the 200mV and 2V ranges; 300V rms continuous).

SETTLING TIME

dB

MODE

0.OldB above

TRMS

RANGE 50Hz* 1OkHz' 20kHz'

200mV

2V - 200V

~ ~~~ ~~ ~ ~ ~ ~~~

750V

'Above

1800

MAXIMUM ALLOWABLE INPUT:

minute on 200mV and 2V ranges, 300V

3dB

BANDWIDTH:

INPUT IMPEDANCE:

1.1MR

paralleled by 75pF on

SETTLING TIME:

dB

MODE

RANGE INPUT lOkHz 20kHz 50kHz 100kHz

2V - 750V 200mV to 750

200mV 20mV to 200mV 0.18

RESOLUTION:

DC

AMPS

RANGE RESOLUTION

200 uA

2mA lOnA 0.3V

20mA 100nA 0.3V

200mA

2000mA

10

"Above 5A derate

*'When properly rereod.

OVERLOAD PROTECTION: mA

10A

Input: 20A for

SETTLING TIME:

TRMS

AC

RANGE BURDEN ZOHz

200pA - 20mA 0.3V

200mA 0.3V

2ooOmA

10

*Above 1800 counts. "1kHz max. Above 5A derate

SETTLING TIME:

RESO- INPUT 24

1

V

v

10

100

1

rV

pV

ImV

OmV

>iGR

>

1GR

iiMR

1OMR

"When properly zeroed.

50Hz.

60Hz

lO00V

1

second to within 3 counts of final reading

(ref:

ma):

Accuracy: &(0.02dB+I count) above -78dBm. Resolution:

0.5%

of range

"OLTsACCURACY (1

2OHz-

1.00+100

1.00+700

1.25+100 *'Above

counts.

3JOkHr typical.

1MR paralleled by less than 75pF

1

second to within

(ref: 600R):

Yr.)

50Hz-

0.35+100

0.75+100 1.0+200 1.8+250 3+400

18000

counts.

750V

rms, rms

200mV,

2V and 2OV ranges. Capacitively coupled.

0.1

%

20Hz- 10kHz- 20kHz- 5OkHz-

V

(-

12 to 59.8dBmj

(-32 tn -12dBmj

2mV to 20mV

(-52 to -32dBm)

1mVto 2mV 2.00 3.00

(-58 to -52dBm)

0.OldB above 0.5% of range.

1

nA

1

PA 0.3V 0.2

10

A

pA

100

pA 0.3V 0.75+15'

0.15%

rdg per amp for self-heating.

15s.

unfused.

1

second to within 3 count5 of final reading.

0.18

0.85

MAXIMUM ACCURACY

VOLTAGE 18"-28'C

BURDEN

Input: 2A fuse (250V), externally accessible.

AMPS

MAXIMUM 18'-28"c

VOLTAGE

A 0.3V

0.8V

1

second to within

-

50Hz 50Hz - lOkHz 10kHz - 30kHz

1.0+100

l.O+IOO

1

OflW

1.5+100**

0.1%

*0.1%.

dc

or

18"-28"C lOkHz

0.6+200

IOOOV

continuous). lO'V*Hr maximum.

of final reading on range.

ACCURACY

0.3V

0.8V

ACCURACY

of final reading.

ACCURACY

*(%rdg+counts)

Hr.,*

0.007+2 0.016+3

0

005+2 0.011+2

0

m6+2 0.015+2

0.006+2 0.015+2

0.007+2 0.015+2

peak ac (less than

on

range.

~~

*(%rdg+counts)

20kHz - 50kHz-

-

50kHz'* 100kHz"

1.5+250 5+400

1.5+250 3+400

peak (less than

on

200V and 750V ranges.

(

+-dBm)

0.18 0.28

0.18

1.10

0.8+100 08+100

08+100

1.0+100'*

0.15%

0.28 0.65

2.00

-

*(%rdg+counts)

0.1

0.2 +I5

(1

Yr.)*

+(%rdg+counts)

rdglamp for self-heating.

10

+15'*

+I5

**

1 Yr.,

seconds per

10

seconds per

0.50

~

-

(1

Yr.)

2 + 250

-

OHMS

RANGE

200

n

2 kR*

20 kQ lOOmR 400pA 4.0V 0.014+2 0.026+2

200 kR*

2MR"

20MR"'

200MR**

'When properly zeroed.

CONFIGURATION: MAXIMUM ALLOWABLE INPUT:

rms

continuous.

OPEN-CIRCUIT VOLTAGE: DIODE TEST:

nominal.

SETTLING TIME:

RESO- NOMINAL ACROSS 24 HI.. 1

LUTION I-SHORT

1mR

1OmR

1

R

10

n

100

R

10

kR

'*Appropriate range selected automatically in MR.

Automatic 2-

Display reads junction voltage

2 seconds to within 3 counts of final reading on range.

OUTPUT

MAX

v

ACCURACY

~

?(%rdg+counts)

UNKNOWN 22 -24°C 18

2mA 2mA 4.0

40pA 4.0V 0.014+2 0.026+2

4

aA

400nA 4.0V

400

nA

or

4-terminal.

450V dc

+5V.

or

peak ac

05V

4.0V

5.0V

up

001

V

0.01

0.02 +2 0.035+2

0.10

2.00

10

seconds per minute. 350V

to 2.2V Test Current: 1.6mA

+2' 002 +3'

+2 0 018+2

+2 0.12 +2 +1

2.00

Yr.

-28°C

GENERAL

DISPLAY:

RANGING:

RELATIVE:

DATA LOGGER

CONVERSION RATE: OVERRANGE INDICATION: "OL" CREST FACTOR MAXIMUM COMMON MODE VOLTAGE: COMMON MODE REJECTION RATIO (1kR

TEMPERATURE COEFFICIENT (Oo-lS0C & 28 -50-C):

ENVIRONMENT:

WARMUP: POWER:

DIMENSIONS, WEIGHT:

ACCESSORIES SUPPLIED:

ACCESSORIES AVAILABLE:

*220,oo0 count LCD.

indication.

dc amps

Model Model 1017: Model 1301: Temperature Probe Model 1600A. High Voltage Probe Model 1641 Model 1651: 50-Ampere Current Shunt Model Model 1682A: RF Probe Model 1684: Model Model 1751: Safety Test Leads Model 1754: Model 1972: Model 1973: IEEE-488 Interface Model 1978: Rechargeable Battery Pack Model 7008-3: IEEE-488 Digital Cable (3 Model 7008-6: IEEE-488 Digital Cable Model 8573.

Auto

or

manual

made with respect to baseline value Front panel annunciator indicates REL mode.

six selectable rates from 3 readingslsecond to ing. Also detects and stores maximum and minimum readings continuously while data logger mode.

SOHr, 6OHz

accuracy specification)/'C.

linearily derate 3% RH/"C, 35"-50"c. Storage: -25' to 60-C.

50-60Hz,

in.

I'ushbutton allows zeroing of

and

MIN/MAX:

(ratio

+0.1%.

Operating: O"-5O0C; less than

1

hour to rated accuracy.

105-125V or 210-25OV (external switch selected).

12V.A. Optional 5-hour battery pack, Model 1978.

X

10%

in.). Net weight 1.8kg

Single Rack Mounting Kit

1010:

Dual Rack Mounting Kit

Kelvin Test Lead Set

:

Clip-On Test Lead Set

1681:

Hard Shell Carrying Case

1685:

Clamp-On Ac Probe Universal Test Lead Kit

IEEE-488 with Analog Output

IEEE-488 Interface for IBM (use with 1972l3)

0.45

in. height; polarity, function, range. and status

on

dc volts, ac volts, and ohms: manual on ac amps and

on

range readings. Allows readings to be

100

reading storage capacity: records data at one of

1

reading;hour

3 readings/second.

of

Greater than 6OdB in ac volts.

displayed.

peak value to rms value),

89mm high X 235mm wide X 275mm deep (31 2 in.

Model 1751 safety te5t leads, instruction manual.

500V

peak

unbalance): Greater than 12OdB at dc,

80%

(3

Ibs., 14

OL

1.

ft

)

(6

it.)

IT

or

by manual trigger-

AC FUNCTIONS:

*

(0.1

X

applicable one year

relative humidity up to 35'C:

90-llOV

3.

available;

+1

X

in

91

4

Specifications subject to change without notice

TABLE

OF

CONTENTS

SECTION 1-GENERAL INFORMATION

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

1.10

2.1

2.2

2.3

2.3.1

2.3.2

2.3.3

2.4

2.4.1

2.4.2

2.4.3

2.4.4

2.5

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

2.7.9

2.7.10

2.7.11

2.7.12

2.8

2.8.1

2.8.2

2.8.3

2.8.4

Introduction Features

Warranty Information ManualAddenda

Safety Symbols and Terms.

...

Specifications Unpacking and Inspection Using the Model Initial Operation Accessories

...........

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

....

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

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

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

.

197

Manual

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

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

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

SECTION 2-BENCH OPERATION

Introduction High Energy Circuit Safety Precautions Preparation For Use

LinePower BatteryPackPower

Battery Charging.

Front Panel Familiarization

Display

Front Panel Controls Input Terminals

Current Fuse Replace ErrorMessages Operating Conditions.

Environmental Conditions

Maximum Allowable Inputs

WarmUp Basic Bench Measurements

PowerUp

Relative Mode

TRMS

Microvolt Measurement Considerations

Resistance Measurements

Current Measurements (DC or TRMS

AC Plus

dB Measurements dB Measurements Considerations and Applicatio

MIN/MAX and

Diode Test

TRMS

AC

Voltage Offset

TRMS

CrestFactor Extended Frequency Response

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

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.....

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...

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...

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

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

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

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

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

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

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

ent

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

AC

Voltage Measurements

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

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

AC)

DC

Measurements

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

100

Point Data Logger Operatio

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

Considerations

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

Measurement Comparison

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

..........

.

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........

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......

1-1

1-1 1-1 1-1

1-1

1-2 1-2 1-2 1-2

2-1 2-1 2-1 2-1

2-2 2-2

2-2

2-2 2-3

2-3 2-3 2-4

2-4 2-4 2-4 2-4 2-4

2-5 2-5

2-6 2-6

2-7

2-8 2-9

2-10

2-13 2-14

2-14 2-14 2-14

i

SECTION

3-

PERFORMANCE VERIFICATION

3.1

3.2

3.3

3.4

3.5

3.5.1

3.5.2

3.5.3

3.5.4

3.5.5

4.1

4.2

4.3

4.3.1

4.3.2

4.3.3

4.3.4

4.3.5

4.3.6

4.4

4.4.1

4.4.2

4.4.3

4.4.4

4.5

4.6

4.7

Introduction Environment itions Recommended Test Equipment

Initial Conditions

..

Verification Procedure

DC Voltage Accuracy Check AC Voltage Accuracy Check

Resistance Accuracy Check DC Current Accuracy Check

AC Current Accuracy Check

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

......

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

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

........

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

...........

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

...........

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

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

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

SECTION 4-THEORY OF OPERATION

Introduction Overall Functional Description

Analog Circuitry.

Multiplexer Input Buffer Amplifier

AC Converter

PIA Display Board

Digital Calibration Model

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

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

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

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

.......

.....

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

.....

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

1978

Battery Option

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

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

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

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

...

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

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

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

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

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

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

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

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

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

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

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

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

......

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

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

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

3-1

3-1 3-1

3-1 3-2

3-2 3-3

3-5

4-1 4-1

4-1 4-1 4-1 4-1 4-1

4-4 4-5 4-5 4-5 4-6 4-6

4-6 4-7

5.1

5.2

5.3

5.4

5.5

5.5.1

5.5.2

5.6

5.6.1

5.6.2

5.6.3

5.6.4

5.6.5

5.6.6

5.6.7

5.6.8

5.7

5.7.1

5.7.2

5.7.3

-___

ii

SECTION 5-MAINTENANCE

Introduction Top Cover Removal/Installation

Battery Pack (Model Line Voltage Selection Fuse Replacement

Line Fuse Replacement

Current Fuse Replacement Front Panel Calibration

Recommended Calibration Equipment

Environmental Conditions

Calibration Jumper

DC Voltage Calibration

AC Voltage Calibration

Frequency Compensation.

Resistance Calibration

Calibration Storage

Troubleshooting

PowerUpSequence Self Diagnostic Program

Power Supply and Battery Pack (Model

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

1978)

Installation

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

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

....

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

.

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

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

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

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

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

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

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

1978)

Checks

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

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

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

....

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

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

.......

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

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

..........

5-1 5-1

5-1 5-2

5-2 5-2

5-2 5-4 5-4

5-4 5-4 5-5

5-5 5-5 5-7

5-7 5-8

5-8 5-8

5-9

ild

5.7.4

5.7.5

5.8

A/D Converter and Display Signal Conditioning

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

Special Handling of Static Sensitive Devices

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

.....

SECTION 6-REPLACEABLE PARTS

.......

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

...

......

...

....

......

5-9

6.1

6.2

6.3

6.4

6.5

Introduction Replaceable Parts Ordering Information Factory Service

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

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

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

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

.......

..

......

..

......

..

......

Schematic Diagrams and Component Location Drawings

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

..

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

..

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

..

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

..

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

...

..

...

..

........

...

......

....

6-1 6-1 6-1 6-1 6-1

...

Ill

LIST

OF

TABLES

2-1

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

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

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

ErrorMessages Model 197 Maximum Allowable Inputs Resistance Range Output Values dB Specification for DC Volts (600fl Ref) dB Specification for AC Volts (600fl Ref) Levels for Other Reference Impedances Comparison of Average and

Recommended Test Equipment Limits for DC Voltage Verification Limits for AC Voltage Verification Limits for Resistance Verification Limits for DC Current Verification Limits for AC Current Verification

Recommended Calibration Equipment DC Voltage Calibration ACVoltageCalibration Resistance Calibration Recommended Troubleshooting Equipment Model 197 Troubleshooting Mode

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

.......

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

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

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

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

TRMS

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

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

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

Meter Readings

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

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

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

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

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

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

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

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

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

Power Supply and Battery Pack (Model 1978) Checks DisplayBoardChecks A/D Converter Checks Model 197 Static Sensitive Devices

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

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

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

.........

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

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

....

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

........

..........

........

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

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

2-4 2-5

2-8

2-10 2-11

2-12 2-15

3-1 3-2 3-3 3-3 3-4 3-6

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

5-8 5-10 5-12 5-12 5-13 5-13

6-1 6-2

6-3

Model197PartsList Display Board. Parts List

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

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

Model 1978 Battery Pack. Parts List

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

6-3

6-6

iv

LIST

OF

ILLUSTRATIONS

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

2-8 2-9

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

3-8

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

Model 197 Front Panel DC Voltage Measurements TRMS AC Voltage Measurements Two Terminal Resistance Measurement Four Terminal Resistance Measurement Four Terminal Zeroing Current Measurements Between 2 Current Measurements up to 2000mA Typical ACV Frequency Response

Connections for Connections for ACV Verification Connections for 200, 2k and 20k Range Connections

for Connections for DC Current Verification (200pA to 2000mA) Connections for DC Current Verification (2000mA to 20A) Connections for AC Current Verification (200pA to 2000mA) Connections for AC Current Verification (2OOOmA to 10A)

Simplified Block Diagram

JFET Multiplexer

Simplified Schematic of the Input Buffer Amplifier

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

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

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

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

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

....

DCV

.........

Verification

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

.........

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

...

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

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

...

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

200k through MU Ranges Verification (2-Terminal)

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

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

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

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

....

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

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

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

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

Input Configuration During 2- and 4-Terminal Resistance Measurements Resistance Measurement Simplified Circuit A/D Converter

...........

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

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

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

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

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

2-2

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

2-9 2-10 2-10

2-15

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

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

5-1 5-2

5-3

5-4

5-5

5-6

5

-7

6-1 6-2

6-3 6-4 6-5 6-6 6-7

Model

DCI

197

I<TJ~:II

ON

Miscellaneous Parts

REVISION

C

........

....

DC Voltage Calibration Configuration AC Voltage Calibration Configuration

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

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

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

200, 2k and 20k Four Wire Resistance Calibration 200k. 2M and 20M

Segment Identification

Display Assembly, Exploded View

Model 1978 Battery Pack, Compone

Two

Wire Resistance Calibratic

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

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

ion Drawing, Dwg Mother Board, Component Location Drawing, Dwg Display Board, Component Location Drawing, Dwg

Mother Board, Schematic Diagram, Dwg Display Board, Schematic Diagram, Dwg

.

No

.

No

197-106

.

197-116

Model 1978 Battery Pack, Schematic Diagram, Dwg

.

No

.

197-100

.

197-110

......

.....

.

1978-106

...........

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

.

No

.

1978-100

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

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

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

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

......

..........

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

. .

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

...

.........

.......

5-3

5-5

5-7 5-7

3-7

5-9

6-1 6-7

6-11 6-13 6-15

6-17

vlvi

SAFETY

PRECAUTIONS

The following safety precautions should be observed before operating the Model

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 Stan-

dards Institue (ANSI) states that a shock hazard exists when voltage levels greater than 30V rms present. measuring.

Inspect the test leads for possible wear, cracks or breaks before each use.

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. Always

disconnect all unused test leads from the instrument.

Do

line (earth) ground. Always make measurements with dry hands while standing on a dry, insulated surface,

capable

A

good safety practice is to expect that a hazardous voltage

not touch any object which could provide a current path to the common side of the circuit under test or power

of

withstanding the voltage being measured.

is

present in any unknown circuit before

If

any defects are found, replace with test

197.

or

42.4V peak are

Exercise extreme safety when testing high energy power circuits (AC line tion.

Do

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

or

mains, etc). Refer to the operation sec-

SECTION

GENERAL INFORMATION

1.1

INTRODUCTION

The Model 197 is a six function,

autoranging digital multimeter with a (Liquid Crystal Display). This normal +-199,999 count

5%

The voltage from 1pV/count to measurements are standard in the Model 197. TRMS ACV capability ranges from IpVlcount to measures resistance from 1mQ to 220MQ on seven resistance ranges. The Model 197 has six current ranges that measure current from 1nA (lO-9A) to 10A.

digit resolution allows the Model 197 to measure

A/D

used in many

1OOOV.

5?h

digit resolution

+-220,000

range is greater than the

count LCD

5?h

digit DMMs.

DC

AC

voltage and current

750V.

The Model 197

1

6.

5%

Digit Resolution-The Model 197 has a +220,000 count A/D that surpasses the more common k199,999 count A/D.

Four

7.

8.

1.3

Terminal Ohms-These terminals are used to eliminate the voltage drop across the current carrying leads.

Sensitivity-The Model 197 has 1pV, ImQ and 1nA sensitivity. The IpV of sensitivity allows minute levels of offset, temperature etc. A 1nA sensitivity allows low current measurements without special equipment. Measure leakage, bias and offset current. A ImQ sensitivity allows easy low resistance measurements.

WARRANTY INFORMATION

The dB function makes of readings into a much smaller scope. The Model 197 dBm measurements are referenced to the standard but can be modified with the use of relative

The Model 197 has two IEEE-488 interface options: The Model 1972 and the Model 1973. These optional interfaces enhance the capabilties of the Model 197 by allowing programmed control over the IEEE-488 bus. The Model 1972 also includes an analog output. The bus commands are the same for each interface and respond to IEEE-488 protocol.

1.2

FEATURES

The Model 197 includes the following features:

Six Measurement Functions-DCV, ACV, DCA, ACA,

1.

OHMS

(REL) Relative Mode-The relative mode allows offsets to

2. be nulled out (e.g. test lead resistance for low resistance measurements) and selects a variety of reference impedances for dB measurements.

Digital Calibration-A non-volatile

3.

tion constants and can be performed from the front panel

or

Data Logger-A data storage buffer is included to allow

4.

up to internally stored at a user selectable rate. The buffer may

be read and controlled from the front panel

IEEE-488 bus. In the talk-only mode, the output rate can also be programmed.

Autoranging-The Model 197 includes a fast autoranging

5.

feature for easier measurements.

and dB all built in.

over the IEEE-488 bus.

100

readings and minimum/maximum readings be

it

possible to compress a large range

600Q

impedance

(REL)

feature.

RAM

stores calibra-

or

over the

Warranty information may be found on the inside front cover of this manual. Should warranty, contact your Keithley representative to determine the proper course of action. Keithley Instruments maintains service facilities in the United States, United Kingdom and throughout Europe. Information con-

cerning the application, operation

ment may be directed to the applications engineer at any of

these locations. Check the inside front cover for addresses.

1.4

MANUAL ADDENDA

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

1.5

SAFETY SYMBOLS AND TERMS

The following safety symbols and terms are used in this manual or found on the Model 197.

The symbol refer to the operating instructions in this manual.

The symbol &n the instrument denotes that a potential

1OOOV

of ard safety practices should be observed when such dangerous levels are encountered.

A

or

more may be present on the terminal(s). Stand-

it

become necesary to exercise the

or

the factory

or

service of your instru-

of

this manual will be

or

on the instrument denotes the user should

1-1

The

WARNING

that could result in personal injury

The

CAUTION

that could damage the instrument.

heading used in this manual explain dangers

heading used in this manual explain hazards

or

death.

NOTE

The Models 1973 and 1972 IEEE-488 interfaces come supplied with their own instruction manual.

1.9 INITIAL OPERATION

1.6 SPECIFICATIONS

Detailed Model 197 specifications may be found preceding

the table of contents of this manual.

1.7 UNPACKING AND INSPECTION

The Model 197 Autoranging Microvolt DMM was carefully inspected, both electrically and mechanically before shipment. Upon receiving the instrument, carefully unpack all

items from the shipping carton and check for any obvious signs of physical damage that may have occurred during transit. Report any damage to the shipping agent. Retain and use

the original packing materials in case reshipment is necessary.

The following items are shipped with every Model 197 order:

Model 197 Autoranging DMM Model 197 Instruction Manual Model 1751 Safety Shrouded Test Leads Additional accessories as ordered.

If

an additional instruction manual is required, order the manual package (Keithley Part Number 197-901-00). The manual package includes an instruction manual and any applicable addenda.

1.8 USING THE MODEL 197 MANUAL

This manual contains information necessary for operating

and servicing the Model 197 Autoranging Microvolt DMM

and the Model 1978 Rechargeable Battery Pack. The informa-

tion is divided into the following sections.

1.

Section 2 contains detailed bench operation information for the Model 197.

2. Section 3 contains the information needed to verify the accuracy of the Model 197. Performance verification can be done upon receipt of the unit curacy of the instrument is in question.

3.

Information concerning theory of operation, maintenance

and servicing is contained in Sections 4 through

or

whenever the basic ac-

6.

Perform the following steps in sequence to acquaint yourself with the basic operation of the Model 197.

Verify that the instrument was not damaged in transit, (see paragraph 1.7).

Carefully read over all safety information (see Section

Basic Operation). Refer to paragraph 2.3 (Line Power) and set the line voltage

switch. Plug the power cord into a properly grounded receptacle. If the Model 1978 is installed the charging circuit is activated.

Acquaint yourself with the front panel controls as follows:

1.

Turn on the instrument using the ON/OFF button. All of

the zeroes are briefly displayed.

2. Connect the supplied test leads to the HI and minals. Connect the red test lead to the HI terminal and

the black test lead to the together.

3. Select AC volts and autoranging by pressing in the AC/DC, V and AUTO buttons. The AC, AUTO and mV annunciators are displayed. Pressing in any of the other range buttons activates manual ranging. This is indicated by the absence of the AUTO annunciator.

4. Select DC volts by releasing (out position) the AC/DC

V

button.

5.

Select the autoranging OHMS by pressing in the AUTO, and symbol is displayed. Press the AC/DC button in (means select AC) and note that the "Err" message is displayed. This indicates an invalid mode.

6.

Select AC or DC current by setting the AC/DC button ac-

cordingly and pressing in the A button. The annunciator

that reflects the selected mode

rent will not autorange. The 10A and

be used on the 10A range.

7. Select dB by selecting AC button. The dB annunciator is now displayed. Press the dB

button to take the instrument out of the dB mode.

8.

The REL (relative) feature can be used with any measurement function: Volts, Amps, Ohms

select the ohms function and autorange. The display reads approximately 000.1403, which is the test lead resistance. Press the REL button. The REL annunciator is turned on and the display reads 000.0003. The relative level of

000.143 will be subtracted from all subsequent measurements. Press the REL button a second time to cancel the REL level.

is still selected. The AC annunciator turns off.

3

buttons. DC must still be selected. The 3 (omega)

LO

terminal. Short the test leads

is

displayed. Note that cur-

or

DC volts and pressing the dB

or

LO

input ter-

LO

terminals must

dB. For example,

2

1-2

9. To activate the minimum/maximum, press and hold in the STO/CLR button. When the reading rate r=O is displayed release the STO/CLR button. The STO annunciator turns on. Press the RCL button and the last data point is briefly displayed

followed by the reading (data). Other data points can be displayed by holding in the RCL button. Turn off the DATA LOGGER by pressing the STO/CLR button again.

100

point DATA

LOGGER

with

1.10 ACCESSORIES

The following accessories can be used with the Model 197

MODEL mount one Model 197 in a standard 5%’’

MODEL 1017 DUAL RACK MOUNTING KIT-Use to mount two Model 197s in a standard

MODEL

temperature probe designed to allow precision temperature

measurements from -55 to 150°C.

MODEL 1600A HIGH measurements to 40kV.

Model 1641 Kelvin Test Lead Set-Special clip leads allow 4-terminal measurements to be made while making only two connections.

MODEL 1651 50-AMPERE CURRENT SHUNT-The external measurements from 0 to 50A

MODEL 1681 CLIP ON TEST LEAD SET-Contains two leads, 1.2m (48”) long terminated with banana plugs and spring action clip probes.

1010

SINGLE RACK MOUNTING KIT-Used to

X

19” rack.

5Y4”

X

19” rack.

1301 TEMPERATURE PROBE-A rugged low cost

0.001Q

VOLTAGE

f

1 % 4-terminal shunt, permits current

PROBE-Extends

AC

or DC.

DMM

MODEL 1751 SAFETY TEST LEADS-This test lead set is supplied with every Model 197. Finger guards and shrouded

of

banana plugs help minimize the chance with live circuitry.

MODEL 1754 UNIVERSAL TEST LEAD KIT-A 12 piece test lead kit, with interchangeable plug-in accessories. Included in the lugs,

two hooks and miniature alligator clips (with boots).

MODEL 1972 ANALOG OUTPUT IEEE-488 INTERFACEThe Model 1972 is an optional IEEE-488 interface that in-

cludes all of the logic necessary to interface the Model 197 to the IEEE-488 bus. The Model 1972 is similar to the Model 1973 however, put is a scaled output that follows the display of the Model

197. The Model 1972 is field installable. MODEL 1973 IEEE-488 INTERFACE-The Model 1973 is an

optional IEEE-488 interface for the Model 197. This interface adds extra versatility to the Model 197 by allowing the transmission of data and commands over the IEEE-488 bus. The interface provides all the logic necessary to interface the

Model 197 to the bus using standard IEEE-488-1978 protocol.

The Model 1973 is field installable.

MODEL 1978 RECHARGEABLE BATTERY PACK-The

rechargeable battery pack allows off line or in the field operation of the Model 197. The pack provides typically five hours operation from full charge. The battery pack contains its own charging circuit and can be recharged within

battery pack is field installable.

MODEL 7008 IEEE-488 DIGITAL CABLE-Useful for con-

necting the 1973 to the IEEE-488 bus. The Model 7008-3 is

0.9m (3

at each end. The Model 7008-6 is 1.8m (6

a standard IEEE-488 connector at each end.

kit

is one set of test leads (1-red, 1-black), two spade

two standard banana plugs, two phone tips (.06 DIA.)

it

contains an analog output. The analog out-

ft.)

in length and has a standard IEEE-488 connector

making contact

10

hours. The

ft)

in length and has

MODEL 1682A RF PROBE-Permits voltage measurements

AC

from 100kHz to 250MHz.

+IdB from 1OOkHz to 250MHz at

calibrated in RMS of a sine wave.

MODEL 1684 HARD SHELL CARRYING CASE-Hard vinyl case, 100mm

has a fitted foam insert with room for the Model 197, an in-

struction manual and small accessories.

MODEL 1685 CLAMP ON rent by clamping on to a single conductor. Interruption of the circuit is unnecessary. The Model 1685 detects currents by sensing the changing magnetic field produced by the current flow.

X

300mm X 350mm (4”

to DC transfer accuracy is

1V,

peak responding,

X

13”

AC

PROBE-Measures AC cur-

X

14”)

MODEL 8573 IEEE-488 INTERFACE-The Model 8573 is an

IEEE-488 standard interface designed to interface the

or

XT

computers to Keithley instrumentation over the IEEE-488 bus. The interface system contains two distinct parts: an interface board containing logic to perform the necessary hardware functions and the handler software (supplied on disk) to perform the required control functions. These two important facets of the Model 8573 join together to give the IBM advanced capabilities over IEEE-488 interfaceable instrumentation.

IBM

PC

1-311-4

SECTION

2

BENCH OPERATION

2.1

INTRODUCTION

This section contains the information needed to prepare and 4. Energize the circuit using the installed connect-disconnect operate the Model 197 as a bench consists of using the Model 197 to perform basic voltage, cur- DMM rent, resistance and

the data logger is covered. The capabilities of the Model 197

can be enhanced with the addition of the Model 1973 or Model 1972 IEEE-488 interface. the Model 1973 Instruction Manual. The optional battery pack (Model 1978) is also covered in this section.

2.2

HIGH ENERGY CIRCUIT SAFETY

dB

measurements. Also, the operation of 5. ~~-~~~~~i~~

DMM.

IEEE

Bench operation

operation is covered in

PRECAUTIONS

To

Optimize safety

distribution circuits, read and use the directions in the following warning.

Dangerous arcs high energy circuit can cause severe personal injury or death. nected to a high energy circuit when set to a current range, low resistance range or any other low impedance range, the circuit is virtuallv shorted. Dangerous arcing can result even when the meter is set range

reduced.

when

measuring

WARNING

of

an explosive nature in a

If

the meter is con-

if

the minimum voltage spacing is

in

to

voltage

high energy third-wire grounded

2. Attach the test leads to the circuit under test. Use ap-

propriate safety rated test leads for this application.

3.

Set the

device and make measurements without disconnecting the

disconnect

6,

Disconnect the

2.3

2.3.1

The Model 197 has a three-wire line cord which mates with

AC

1.

Set the LINE VOLTAGE switch on the back of the instrument to correspond to line voltage available. Ranges are 105V-125V or 210v-250V 50/60Hz

2. Plug the power cord into a properly grounded outlet.

DMM

to the proper function and range.

~~

.

the

device.

test

circuit

leads

using the installed connect-

from

the

circuit

under

PREPARATION FOR USE

Line

Power

Connect

line

power

as

follows:

CAUTION Connect only to the line voltage selected. Application damage the instrument.

of

incorrect voltage can

AC.

the

instrument

test,

to

When making measurements in high energy circuits use test leads that meet the following requirements:

Test leads should be fully insulated. Only use test leads that can be connected to the circuit (e.g.

alligator clips, spade lugs, etc.) for hands-off measurements.

Do not use test leads that decrease voltage spacing. This diminishes arc protection and creates a hazardous condi-

tion.

Use the following sequence when testing power circuits:

1.

De-energize the circuit using the regular installed connect-

disconnect device such as the circuit breaker, main switch, etc.

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

NOTE

Although the Model 197 is specified at 50 and 60Hz the instrument may be operated and 440Hz.

at

400Hz

2-1

2.3.2 Battery Pack Power

The Model 197 may be operated from rechargeable sealed

nickel-cadmium batteries contained in the optional Model

1978 Rechargeable Battery Pack. The battery pack will operate the Model 197 for typically five hours. (NOTE: The Model 197 uses the most power on the amps function and also

2OOQ,

in the

turns on when the charge is insufficient to maintain accurate

readings. Refer to paragraph 5.3 for installation procedures.

2kQ or 750VAC ranges). The BAT annunciator

2.3.3 Battery Charging

If the battery pack is not maintaining a charge

10

for five hours after a full following.

A. Disconnect the Model 197 from line power.

B.

Turn on the Model 197 and leave discharge the battery pack.

C. Connect the Model 197 to line power and charge the

10

battery pack for

D.

Repeat steps A through C three more times. The battery pack should again be good for typically five hours.

3.

When the Model 197 is in use on line power, the battery charger maintains a trickle charge on the battery pack.

hours with power off.

hour charge cycle, do the

it

on to completely

(BAT

off)

After the Model 1978 is installed in the Model 197

charged and recharged as follows:

1.

Connect the instrument to line power as described in paragraph 2.3.1.

2.

With the power switch off, the battery charge circuitry is automatically energized to charge the battery at the max-

imum rate. When the battery pack is first installed, or

is completely discharged, allow

of

10

hours.

For maximum battery efficiency only charge the battery pack after charged (BAT annunciator on). Do not make measurements with BAT annunciator on as the readings may be erroneous.

it

has become completely dis-

NOTE

it

to charge for a minimum

-1

it

197

AUTORANGING

can be

if

NOTE

The

IEEE

options (Model 1972 and Model 1973)

do not run off of battery power.

2.4

FRONT

it

Figure description of the display, front panel controls and input terminals.

2.4.1

The Model 197 has a The minus sign is displayed. The plus sign is implied by the absence of the minus sign. The following annunciators are displayed on the

2-1,

Display

MICROVOLT

PANEL FAMILIARIZATION

and the following paragraphs, provide a brief

5%

digit liquid crystal display (LCD).

LCD.

DMM

~

I

2-2

w

200m

*

QSENSE

u

I

BAT-Low battery indicator for the Model 1978.

AC-AC selected (DC implied by the absence of the AC annunciator).

AC/DC-This button is used along with the volts

(A),

rent AC, releasing (out) this button selects condition. See Table 2-1.

and dB functions. Depressing (in) this button selects

DC.

AC

!2

(V),

cur-

is invalid

or

mV

O,

p,

RMT

IEEE-488 bus (Model 1973

C-Model 197 in calibration mode.

AUTO-Autorange.

REL-Relative.

dB-Decibel measurement mode.

STO-Data being stored.

RCL-Data being recalled. RCL flashes when buffer is full

during logging cycle.

V-Millivolts or volts.

kO or MO-Ohms, kilohms

mA or A-Microamps, milliamps

(REMOTE)-Model 197 being controlled over the

or

megohms.

or

amps.

or

Model 1972 installed).

2.4.2 Front Panel Controls

ON/OFF-Pressing this button turns on the Model 197.

Releasing (out) this button turns the instrument off.

REL-(RELATIVE)-This button allows readings to be made

of

with respect to any baseline value. Also allows zeroing

range readings. See paragraph 2.7.2 for more detailed infor-

mation on

dB-This button selects the dB function and is used along with the ACV or DCV function. Measurements are made in dBm referenced to voltage level the OdB reference point for dB measurements.

DATA LOGGER and MIN/MAX-100 reading storage capacity; records data at one reading/second

(r=6).

readings continuously while in the data logger mode.

REL.

600O.

REL

can be used to make any

of

seven selectable rates from

to

1

reading/hour

Also detects and stores maximum and minimum

or

by manual trigger

on

V-Depressing this button selects the volts function.

0-Depressing this button selects the ohms function. The AC/DC button must be released (out).

A-Depressing (in) this button selects the current function. Up to 2A on red and black input jacks and up to 10A with the black and white input jacks. Refer to paragraph 2.4.3.

RANGE BUTTONS

1.

Depressing AUTO button allows volts and ohms to autorange. In current, autorange function for current.

2.

Manual ranging propriate range button.

it

selects the 10A range. There is no

is

accomplished by depressing the ap-

2.4.3 Input Terminals

The input terminals are intended to be used with safety shrouded test leads to help minimize the possibility with live circuits. Safety shrouded tests leads (Model

are supplied with the Model 197. Always disconnect all un-

from

used test leads

HI

and

LO

INPUT (Red and Black)-Use this pair of ter-

minals

1OA

measuring current up to 10A (up to 20A

OHMS Sense HI and LO-Use this pair of terminals along with HI and

3

for

all volt, ohm, milliamp and dB measurements.

and

LO

(White and Black)-Use this pair of terminals for

LO

the instrument.

for

15 seconds).

input for four wire resistance measurements.

2.4.4 Current Fuse Replacement

of

contact

1751)

1.

STO/CLR-Pressing this button initiates the logging se-

a

quence. Pressing this button data logger. For

reading is desired, press the STO/CLR button.

2. RCL-Pressing and holding in this button scrolls the data pointer. To read the data at a certain point, simply release

the button. The logged readings are stored in buffer locations

01

to 102. They are depicted on the front panel as

follows: Buffer location

r=6

rate (manual trigger) every time a

#1

second time turns off the

is represented

___

by n=01.

-

Tne current fuse protects the 200pA through 2000mA ranges from an input current greater than 2A. To replace the current fuse, perform the following steps:

NOTE

The front panel current fuse (F101) is rated at

2A. With a 220,000 count display, the 2A range

can momentarily (approx. one minute) read

2.2A before the fuse will blow. This range will not harm the instrument.

1.

Turn off the power and disconnect the power line and test

leads.

2. Place the end of a flat-blade screwdriver into the slot in the fuse holder on the front panel. Press in slightly and rotate the fuse carrier one quarter turn counterclockwise. Release pressure and remove the fuse carrier and the fuse.

3. Remove the defective fuse and replace type: 2A, 250v, 3AG, normal-blow (Keithley part number FU-13)

or

equivalent.

10%

over-

it

with the following

of less than 80% up to humidity 3% per "C up to 50°C. subjected to extremes of temperature, allow sufficient time for internal temperature Typically, (18°F) out of the specified temperature range.

it

takes one hour to stabilize a unit that is 10°C

35°C.

For ambient above 35°C derate

If

the instrument has been

to

reach environmental conditions.

2.6.2 Maximum Allowable Inputs

Table 2-2 lists the maximum allowable inputs for the Model

197.

CAUTION

Use only the recommended fuse type. If a fuse with a higher current rating is installed, instrument damage may occur.

2.5

ERROR MESSAGES

Table 2-1 lists the error messages associated with basic front panel operation. Note that the instrument has other messages that are discussed in the appropirate sections

of the manual.

a

number of

2.6 OPERATING CONDlTlONS

2.6.1 Environmental Conditions

All

measurements should be made at an ambient temperature

within the range of 0°C to 50°C, and with a relative humidity

Table

2-1.

2.6.3 Warm Up

The Model 197 requires one hour for warm rated accuracy.

up

2.7 BASIC BENCH MEASUREMENTS

Basic measurement techniques for using the Model 197 to measure AC and DC volts, resistance,

and

dB

are covered in the following paragraphs. ed is the operation of the minimum/maximum and data logger.

WARNING Before operating the Model previously mentioned safety precautions. When testing high energy power circuits follow the instructions found in paragraph

2.2.

Failure to observe these and other safe-

Error

Messages

AC

197,

observe all

and

Also

to achieve

DC

current

includ-

100

point

2-4

3isplay

LC

Err

--

~

Message

I

~

Q11(

Invalid D Function

Comments

Model 197 locks up. See Section 5 for troubleshooting information. Model 197 locks up, but operation can be restored by pressing

any one of the four momentary pushbuttons. If restored, calibration is invalid as indicated by the flashing "C" annunciator. See Section

Overrange input applied to the Model 197. Leading minus sign indicates that input signal has a negative value.

"AC" and (out) AC/DC Dushbutton.

5

for troubleshooting information.

"Q"

annunciators flash. Correct problem by releasing

2-3

Table

2-2.

Model

197

Maximum Allowable Inputs

-7

Function

DCV

ACV

DCA, ACA

Q

ty precautions mentioned in this manual could result in severe injury or death.

The

LO

terminal on the Model 197 is designed to float above

earth ground to avoid ground loop problems.

WARN I NG

Hazardous voltage may be applied to the

LO

terminal. The maximum allowable voltage between the ground is which could present a shock hazard, may

occur

Do not exceed the maximum input limits shown in Table

2.7.1

Power

The software revision level of the Model 197 can be displayed upon power up by running the diagnostic program. See Section

ance, for more information.

Turn on the Model 197 by pressing in the

All

zeroes are briefly displayed before going into the measure-

ment mode.

If

the Model 197 does not enter the measurement

mode, refer

if

the

Up

500V.

500V

to

LO

Destruction

maximum is exceeded.

CAUTION

2-2.

NOTE

section 5.7.1.

Ranges

200mV, 2V

20-1OOOV 1000VDC or peak AC.

i

~OO~V,

'

20-75OV

~

200p-2000mA

I

1 OA

1

terminal and chassis

All

of

5,

1

'

~

2v

insulation,

Mainten-

ON/OFF

Maximum Allowable Inputs

1000VDC or peak AC for less than 10sec per minute.

300~rms continuous.

750Vrms, 1OOOV peak for less than 10sec per

minute. 300Vrms, continuous. lO7*Hz maximum. 750Vrms, IOOOV peak. l07.H~ maximum.

2A, 250VDC or

10A continuous; 20A for 15sec (unfused).

450V peak AC 350Vrms continuous.

switch.

rrns

(fuse protected).

or

DC,

10

seconds per minute,

2.7.2

3.

Relative

When the relative mode is selected with an on-scale reading on the display the following occurs:

1.

The REL annunciator is displayed.

2.

The next reading is stored. This reading is algebraically subtracted from all subse-

quent readings and displayed.

A

REL level can be established for any measurement function (Volts, Ohms, Amps and dB) and function. Changing functions will not affect a already established. However, any function) the previous ple, place the Model 197 in the ohms function and select the

200Q

range. Short the test leads and press the REL button.

Note that the REL annunciator is on. Select DCV and note

that the

REL

that the

REL

back

celled.

It

REL

braically subtracted from all subsequent readings

function.

Once a that stored level will be the same regardless of what range the Model 197 is on. REL level on the 20VDC range, other DCV ranges.

REL

level established for DCV. Switch back to ohms and note

REL

level of

to

ohms and note that the

is important to remember what the

function establishes a baseline. That baseline

REL

Mode

is

effective only on that

if

another

REL

level is cancelled.

annunciator is off, indicating that there is not a

level is still there. Again,

+lV.

The REL annunciator turns on. Switch

REL

level for ohms

REL

level is established for a measurement function,

For

example,

if

+1V is established as the

+

1V

is

I

1

I

REL

level is set (on

For

exam-

go

to

DCV and set

is

function does. The

is

for

also the REL level

level

a

can-

alge-

that

for

2-5

The dynamic range means that

applying +1.99999V to the input displays +3.99999V. Once the REL level is established, that level is algebraically subtracted from the input signal.

+

1

.OOOOOV

f2.OOOOOV level displays a

if

of

the display is

a

REL

level of -2.OOOOOV is established, then

REL level is established, then applying a

+1.OOOOOV

-+400,000

For

example:

level.

counts. This

if

a

7

The instrument accepts a +220,000 count input before going

(OL).

into the overrange condition

REL

level is established and 1.50000V is applied. The instrument displays +2.500000V. If the input is 2.20000V the instrument overranges.

2.7.3

The Model 197 can make DC voltage measurements between

DC

Voltage Measurement

1pV and

1.

2. Select the DCV function.

3. Select a range consistent with the expected voltage. For

IOOOV.

Connect the test leads to the of the Model 197.

automatic range selection, press in the

To prolong instrument life, manual ranging is

recommended for routine measurements above 200v.

The basic procedure is as follows:

NOTE

For example:

HI

and

LO

AUTO

-1.OOOOOV

INPUT

button.

terminals

CAUTION.

o/

I

The 200mV DC range and the 2000 range require zero to be set in order to achieve rated accuracy.

2.7.4

The Model between

1.

2. Select the ACV function.

3.

4.

MODEL

Figure

TRMS

Connect the test leads Model 197.

Select a range consistent with the expected voltage. automatic range selection, press in the AUTO button.

Connect the test leads to the source as shown in Figure 2-3.

197

2-2.

AC

197

can make TRMS AC voltage measurements

1pV

and 750V. To measure AC proceed as follows:

INPUT RESISTANCE = 10M. EXCEPT

>

lOOOM

DC

Voltage Measurements

to

the

HI

on

1OOOV

MAXIMUM INPUT

200mV

and

LO

and

2V

terminals

RANGES

of

the

For

4.

Connect the test leads to the source as shown in Figure 2-2.

If

the positive source terminal is connected to the

minal of the instrument, the display shows a negative

If

value.

LO

5. Observe the display; higher range until a normal reading is displayed. Always use the lowest possible range for the best resolution.

6.

Take the reading from the display.

The term "when properly zeroed" means that the user must

establish a proper baseline for subsequent measurements on that range. To zero the Model 197 use the following pro-

cedure:

1.

Short the INPUT

2. Wait until the displayed reading settles. Noise and thermal

emfs may require a few moments

3. Press the

2-6

the negative source terminal is connected to the

terminal, the display shows a positive value.

If

the

"OL"

message is shown, select a

HI

and

LO

test leads together.

to

settle out.

REL

button.

LO

ter-

NOTE

There is a small amount of offset (typically 50 counts

tion. this is that the offset is generally negligible as compared to the input signal.

offset applied signal displayed reading =\(20mV)2

This offset is seen as the last digit which is not displayed on the Model 197. Therefore, the offset is negligible.

5.

Observe the display,

higher range until a normal reading is displayed. Always use the lowest possible range to obtain the best resolution.

or

less) present when using the

Do

not REL this level out. The reason for

=

22pV

=m-+484

=

.0200000121

=

20mV

x

10-iZ

if

the

AC

For

example:

+

(22pV)Z

"OL"

message is shown, select a

func-

6. Take the reading from the display

NOTE

See paragraph When measuring leads from the OHMS SENSE terminals.

-INPUT MODEL

197

2.8

for TRMS considerations.

AC

signals disconnect any test

IMPEDANCE

BY

<

75pF

=

IMR

SHUNTED

R,

=

parallel combination of source resistance and input impedance.

e, = Johnson noise of the source resistance.

on

Even

is

Thus, for an R, of inherent 1.5pV peak to peak. Beyond to R, becomes a limiting factor in the measurement. Therefore, it is recommended that ments R, be kept relatively 10~7,

As

(due to Johnson noise of the source resistance) assume that the

Model 197 is connected to a voltage source with an internal resistance of p-p noise voltage generated over a bandwidth

most sensitive range, the noise due to the current

not appreciable until R, reaches approximately

OQ

to

lMQ,

the noise at the input is the

1MQ

the noise due

for

sensitive measure-

if

possible below

an example of determining e, noise voltage generation

1MQ.

At

a

=

e,

e, = 6.35

room temperature

6.35

X

10-10

X

lO-lO\r(lx

\J

R

X

10m

of

20°C

of

f

1MQ.

(293K),

1Hz

will be:

lMQ.

the

Figure

2.7.5

Accuracy Considerations-For sensitive measurements, other external considerations besides the Model

accuracy. Effects not noticeable when working with higher voltages are significant in microvolt signals. The Model 197 reads only the signal received at its input; therefore, portant that this signal be properly transmitted from the

source. The following paragraphs indicate factors which af-

fect accuracy, noise, source resistance, thermal emfs and stray pick-up.

Noise and Source Resistance-The limit of resolution in measuring voltages with the Model 197 is determined by the noise present. The displayed noise of the Model 197 is 1.5pV peak to peak. This noise is inherent in the Model 197 and is

the minimum amount present in all measurements. The 1.5pV

of noise is due to the instrument voltage noise. The noise at the Model 197 input increases beyond this minimum when the noise current passes through a resistor thus generating a voltage noise. The total noise becomes a function of the

source resistance and is given by the equation:

2-3.

TRMS

AC

Voltage Measurements

Microvolt Measurement Considerations

197

will affect the

it

is im-

=

en2

+

n2

(inRs)2

+

er2

e, = 0.635pV

Thus

it

is clear that optimum microvolt measurements with

the Model 197 are possible with source resistances as high as

1MQ.

However, this resolution will not be realized unless

shielding is employed.

Shielding-The Model 197 is insensitive

DC

superimposed upon a However, with the Therefore, shielded and the shield connected to the Model 197 ground

(particularly for low-level sources). Improper shielding can

cause the Model 197 to behave in one

ing ways:

1. Unexpected offset voltages.

2.

Inconsistent readings between ranges.

3.

Sudden shifts in reading.

To minimize pick up, keep the voltage source and the Model

197 away from strong

duced due to magnetic flux is proportional to the area

loop formed by the input leads. Therefore, minimize the loop area of the input leads and connect each signal at only one point.

AC

voltages which are extremely large compared

DC

signal may erroneously produce

if

there is

AC

signal at the input terminals.

interference, the circuit should be

AC

magnetic sources. The voltage in-

to

AC

voltages

a

DC

output.

or

more of the follow-

of

the

where n

=

total noise input.

=

input voltage noise of the Model 197.

en

in

=

input current noise.

Thermal EMFs-Thermal emfs (thermoelectric potentials) are

generated by thermal differences between two junction dissimilar metals. These can be large compared which the Model 197 can measure. Thermal emfs can cause the following problems:

to

the signal

of

2-7

1.

Instability

2. The reading is sensitive to (and responds to) temperature changes. This can be demonstrated by touching the circuit, by placing a heat source near the circuit pattern of instability (corresponding to heating and airconditioning systems or changes in sunlight).

3. To minimize the drift caused by thermal emfs, use copper

leads to connect the circuit to the Model 197. plug is generally sufficient and generates just a few microvolts.

is about the best for the application. The leads to the input may be shielded Shielding.

4.

Widely varying temperatures within the circuit can also

create thermal emfs. Therefore, maintain constant temperatures to minimize these thermal emfs. box around the circuit under test also helps by minimizing air currents.

5. The REL control can be used to null out constant offset

voltages.

2.7.6

The Model 197 can make resistance measurements between

1m3 and 22OM3. The 2M3, 20MQ and 200MQ ranges autorange when the provides automatic selection of 2-terminal resistance measurements. This means that leads are not connected, the measurement is done &terminal.

If

the sense leads are connected the measurement is done 4-terminal. For 4-terminal measurements, rated accuracy can be obtained as long as the maximum lead resistance does not exceed the values listed in Table 2-3. For 2-terminal 4-terminal measurements on the 2003 range, zero must be set by the REL function to obtain rated accuracy. For best results

on the 2003, 2k3 and 2Ok3 ranges, it is recommended that 4-terminal measurements be made to eliminate errors caused by the voltage drop across the test leads that occurs when 2-terminal measurements are made. To make resistance

measurements, proceed as follows:

or

zero offset is much higher than expected.

A

clean copper conductor such as

or

unshielded, as necessary. Refer to

Resistance Measurements

M3

button is selected. The Model 197

or

by a regular

A

banana

#lo

bus wire

A

cardboard

or

4-terminal

if

the ohms sense

or

1.

Connect the test leads to the HI and If four-wire measurements are to be made, connect an additional set of leads to the OHMS SENSE terminals.

NOTE

The Model 1641 Kelvin test lead kit is ideal for low resistance 4-terminal measurements.

2. Select the ohms function.

3.

Select a range consistent with the expected resistance. desired, use the autorange mode for automatic range selection.

4.

If

readings are to be made on the 2OOQ range, zero the instrument to obtain rated accuracy. To zero the instrument for resistance measurements: Short the test leads together after disconnecting them from the measured circuit: 4-wire measurements are to be made, short leads as shown in Figure 2-6, allow the reading to settle

REL

then press the

5.

For 2-wire measurements connect the instrument as shown in Figure 2-4. For 4-wire measurements, use the connections shown in Figure 2-5.

The maximum input voltage between the

HI

and LO INPUT terminals is

peak AC for

RMS

values or instrument damage may occur. Table various resistance ranges.

Incorrect readings will result if the resistance being measured is part circuit.

6. Take the reading from the display.

continuous. Do not exceed these

2-3

button.

CAUTION

10

seconds per minute,

shows the current output for

CAUTION

LO

450V

INPUT

all

DC or

350V

of

a live

terminals.

four test

If

if

2-8

Range

200

2k

20 k

,

200 k

200M

tesolutior

lm3

1

OmQ

1

OOmQ

1Q

10

0

100

Q

10

k3

Table

I-S

hort

2mA 2mA

400pA

40 pA

4 PA

400 nA 400 nA

2-3.

Resistance Ranges

Across

Unknown

4.0V

5.0V

Maximum Test Lead

Resistance for

(1

Count Error

10

(Q)

32

100

320

Ik

3.2k

10k

NOTE

It

is helpful to shield resistance greater than 106Q

(1MQ)

resistance in a shielded enclosure and electrically connect the shield to the the Model 197.

-

if

a stable reading is expected. Place the

LO

input terminal of

OPTIONAL SHIELD

__

RESISTANCE

2.7.7

Current Measurements

(DC

or TRMS

AC)

The Model 197 can make DC or TRMS AC current measurements between 1nA and 10A (20A for the expected current level is in question, make the initial measurement on the 10A range. This helps prevent inadvertent blowing of the 2A current fuse which is located on the front panel.

I

NOTE

For routine measurements above 10A recommended that the Model 1651 50A shunt be used.

15

seconds).

it

If

is

Figure

MODEL 197

2-4.

Two

MODEL 197

Figure

CAUTION: MAX INPUT

or PEAK AC for lOsec/min, 350V

[

RMS CONTINUOUS

=

450VDC

Terminal Resistance Measurement

OPTIONAL SHIELD

I-----

CAUTION: MAX INPUT = 450VDC

or

pk

AC for 10sec/min, 350V RMS

CONTINUOUS.

2-5.

Four Terminal Resistance

-

---

Measurement

1.

For current measurements between 2000mA and 20A.

to

A. Connect the test leads

the Model 197. Refer

The test leads used must be rated to handle 20A. Twist the wires as shown in Figure 2-7 minimizing external fields which could affect the

I

Model 197 or other equipment. Also, keep the test leads as short as possible voltage drop.

B.

Select the ACA or DCA function.

C. Select the 10A range. The amps function does not

autorange.

D. Connect the test leads to the current source as shown in

Figure 2-7 and take the reading from the display.

Up to

5A

may be applied continuously without degradation of the measurement due to self heating effects. Above amp for self heating, refer to specifications that precede Section 20A, specified accuracy can only be obtained when measurements are limited to a maximum of

15

seconds.

1.

the 10A and

to

Figure 2-7.

NOTE

5A

derate

For

currents between 10A and

to

0.15%

LO

terminals

to

help in

minimize

rdg per

of

INPUT

LO

OHMS SENSE LO OHMS SENSE HI SHORT

Figure 2-6. Four Terminal Zeroing

2.

For

current measurements up to 2000mA:

A.

Connect the test leads to the INPUT minals

B.

Select the ACA or DCA function.

C.

Select an appropriate range for the expected current.

The current function does not autorange.

of

the Model 197.

HI

and

LO

ter-

2-9

D.

Connect the test leads to the current source as shown in Figure 2-8. select a higher range until a normal reading Use the lowest possible range to obtain the best resolution.

E.

Take the reading from the display.

If

an overrange indication is displayed,

is

shown.

1.

Measure and record the cribed in paragraph 2.7.4.

2. Measure and record the paragraph 2.7.3.

3. Compute the rms value from the following equation:

Em,

TRMS

DC

component as described in

=UE~D~

+

AC component as des-

E~AC

-CAUTION:

MODEL

197

MAX INPUT

=

IOA

Figure 2-7. Current Measurements Between

2000mA and 20A

2.7.9

dB

Measurements

The dB function makes of

readings into a much smaller scope. The relationship bet-

ween dB and voltage can be expressed by the following equa-

tion.

it

possible to compress a large range

VIN

dB

=

20

log-

VREF

Tables 2-4 and 2-5 list the AC volts.

The Model 197 can make

600Q

standard relative feature allows measurements in

impedance.

The basic procedure

mode is

button. Note that once

pressing in the

to

impedance

first select AC or DC volts and then press the

Q

or A function pushbuttons will turn

dB

specifications for DC volts and

dB

measurements referenced to the

or

to other impedances. The

dB

independent

for

placing the instrument in the dB

dB

is selected

(dB

annunciator on),

dB

off.

of

Figure

2.7.8 AC

Use the Model 197 to measure TRMS on a signal which has both AC and

2-10

2-8.

Current Measurements up to 2000mA

Plus

DC

Measurements

DC

components.

Table 2-4. dB Specifications for DC Volts

(600Q

Linear

~ Counts

10-99 100-999 1000-9999 10000-220,OOO

Ref)

Resolution Accuracy

IdBrn

0.ldBrn

0.OldBrn +O.ldBrn

0.01 d

Brn

k

2dBrn

k

-t

0.02dBrn

IdBrn

typical

Table

dB

Range

200mV

2-5.

M

dB

de (Ref:

InDut

1mV

(-58

to

2mV

(-52

to

20mV

(-32

to

Specifications for

60001

20Hz-

10kHz

to

2mV

-52dBm)

to

20mV

-32dBm)

to

200mV

-12dBm)

2.00

0.85

0.18

AC

Volts

Accuraci

10kHz-

2OkHz

3.00

1.10

0.18

(600n

(

k

dBw

ZOkHz-

50kHz

-

2.00

0.28

Ref)

5OkHz100kHz

-

0.65

ZV-75OV

dBm

Measurements with

dBm is defined as decibels above The standard reference impedance of the Model 197 is 6000. What that means is that the Model 197 is designed to read OdBm when the voltage needed to dissipate 1mW through a

600a

impedance is applied to the Model 197. That calculated voltage level is 0.7746V as derived from the basic power equation.

~~

E=h’.R

E

=q0--3

E

=

0.77456V

Thus with a 6000 reference impedance the Model 197 will read OdBm whenever 0.7746v is applied.

Do

not confuse reference impedance with input

impedance. The input impedance

ment is not modified in the dB mode.

To

make dBm measurements referenced

follows:

-

W.6000

600a

Reference Impedance

NOTE

200mV

1-12

or

below a 1mW reference.

of

to

750V

to

+59.8dBm)

the instru-

6000, proceed as

0.18

dBm Measurements with Other Reference Impedances

dBm measurements can be made with other reference impedances. The most convenient method for using other reference impedances is to algebraically subtract the calculated dB offset for the desired reference impedance from

the reading on the display of the Model 197. Table 2-6 lists common reference impedances and the corresponding offset values. The following equation can be used to calculate the

offset the offset for impedances not listed in Table 2-6.

To

pedance, proceed as follows:

1.

2. Calculate

3.

0.18

make dBm measurements referenced to another im-

Choose the desired reference impedance.

desired reference impedance. Determine dBm at the desired reference impedance as

follows:

Example: Make dBm measurements references to a 1000 reference impedance.

0.28

Offset (for dBm) = 10 log----

or

look up the offset value in Table 2-6 for the

dBm (at ref

0.50

Z)

=

197 reading - offset

New ref

600Q

Z

1.

Connect the test leads to the INPUT of the Model 197.

2. Select the ACV

3.

Select autorange for optimum resolution.

4.

Press the dB button.

5.

Connect the test leads to the voltage source.

6. Make the dBm reading from the display.

or

DCV function.

HI

and

LO

terminals

A.

1000 not listed in Table 2-6 calculated as follows:

Offset

B.

Subtract -7.78 from all subsequent displayed readings on the Model 197.

=

10 log

Offset = -7.78dB

so

the offset must be

(z

)

2-1 1

dBm measurements, referenced to another impedance, can be

read directly from the display of the Model 197 by utilizing the

REL

feature, and an accurate voltage source. The basic

procedure is as follows:

1.

Calculate 2-6) for OdBm at the desired reference impedance.

2. Input that voltage level to the Model 197.

3. With the Model 197 in the

4.

dBm measurements referenced to the desired impedance

can now be read directly from the display

197.

dBW

dBW is defined as decibels above

reference. The procedure

paragraph 2.7.9 step 2. reference point is OdBW (1W) rather than OdBm (1mW).

dBV

Measurements

dBV is defined as decibels above or below 1V (OdBV point).

This is a voltage relationship independent of impedance. The

basic procedure is to simply subtract 2.22 dB (Table 2-6) from all subsequent displayed readings on the Model 197.

Relative

Just about any voltage level within the measurement limit of

the Model 197 can be established as the OdB point. The basic procedure is to establish the level as the OdB point by using REL and make the desired dB measurements.

2.7.10

or

look up the equivalent voltage level (Table

dB

Measurements

dB

Measurements

mode, press the

or

is

the same as that found in

The only difference is that the

REL

of

the Model

below a one watt

dB Measurement Considerations and

button.

Applications

1.

Typical Instrument Performance

Typically, the Model 197 will perform better that its published dB specification. The following example will lustrate this point:

A.

Using the Model 197 in the dB mode (6003 ref) measure a ImV communications field). Typically, the Model 197 will read -57.7dBm.

The calculated dBm level for that source is -57.8dBm.

B.

The O.1dBm error is considerably better than the

C.

+

to cover worst measurement conditions.

RMS,

1kHz source (common application in the

2dBm specification. The specifications are intended

il-

Table

2-6.

Levels for Other Reference Impedances

I

Reference 1 Reference Voltage

'

Impedance

I

~

Offset

Vref

Vref,

(Q2)

150

300

for for

(for

8 50 75

OdBm OdBW

dBm) = 10

Level for:

OdBm OdBW

0.0894 2.828

0.2236

0.2739

0.3873

0.5477

0.7746 1

.oooo

=

\

ZREF

~

log

I

'

.

Offset

(600Q

Ref)

OdBm OdBW

-

18.75 11.25

-

10.79

-

9.03

-

6.02

-

3.01

0.00

I

2.22

Cblb:!)

Offset

2. Measuring Circuit Gain/Loss

3. Measuring Bandwidth

(for

dBW) = 10

Any point in a circuit can be established as the OdB point.

Measurements in that circuit are then referenced to that point expressed in terms of gain (+dB) or set the OdB point:

A. Place the Model 197 in volts, autorange and dB.

B.

Connect the Model 197 to the desired location

circuit. C. Press the D. Gain/Loss measurements can now be made referenced

to the OdB point.

The Model 197 can be used to determine the bandwidth of

amplifier as follows:

an

Connect a signal generator to the input of the amplifier.

A.

Set the Model 197 to ACV and autorange.

B.

Connect the DMM and a frequency counter to the load

C.

of the amplifier.

Adjust the frequency of the signal generator until a

D.

peak AC voltage reading is measured on the Model

197.

Press the dB button and then press the

E.

OdB point

Increase the frequency input until the Model 197 reads

F.

-

3.00dB. The frequency measured on the frequency

counter is the high end limit of the bandwidth. Decrease the frequency input until the dB reading again

G.

falls to -3dB. The frequency measured on the signal generator is the low end limit of the bandwidth.

REL

is

log

(zR:ooQ

button. The display will read OdB.

now established.

)

REL

-30dB

loss

(-dB). To

button. The

in

the

I

2-12

4.

Determining The Q of a tuned circuit can be determined as follows: A. Determine the center frequency and bandwidth as ex-

plained in paragraph 2.7.10 step

B.

Calculate Q by using the following formuala:

Q

=

Center Frequency/Bandwidth

3.

The logging cycle can be terminated at any time by pressing the STO/CLR button. This shuts off the data logger. However, data is retained and can be recalled at any time as long as the instrument remains on. In the RCL and the STO/CLR button to terminate the data logger cycle.

2.7.11 MIN/MAX and 100 Point Data Logger Operation

The data logger can store up to minimum and maximum readings recorded during the period that the data logger is active. The stored at one of seven selectable rates from three per second

to one reading per hour. Also, manual triggering is available (r=6). In the r=6 mode, one reading is stored every time the STO/CLR button is pressed. Readings for minimum and maximum are sampled at the rate of three per second regardless of the selected rate. The procedure for operating the data logger is as follows:

Connect the desired measurement configuration to the

1.

Model 197. Make sure that the controls of the Model 197 are set appropriately. the display.

Logging Data:

2. A. Press and hold the STO/CLR button. The following

reading rates will scroll on the display: rate/ meaning

r

=

0

(every reading)

r=l

(1

rdg/sec)

r=2

(1

rdg/lo sec)

r=3

(1

rdg/min)

r=4

(1

rdg/lo min)

r=5

(1

rdg/hour)

r=6 (Irdg every time STO/CLR is pressed)

There is no need to select a rate

minimum/maximum readings are desired. Press the STO/CLR button to start the logger.

NOTE

100

readings and store the

100

points of data are

if

just

In the store mode

is full readings are continuously updated. When the store mode turned off the minimum and maximum readings are not updated.

3.

(100

Data Retrieval-Data can be retrieved at any time, but a flashing number of readings

A. Press and hold in the RCL button. The display scrolls

through the data points and MIN/MAX (LO/HI). The first data point displayed is the last stored reading. The next two data Doints are the during that logging cycle. Notice that the longer the

RCL

B.

Release the note the reading (data) on the display. The data pointer can be incremented by steps of one by momentarily holding in the RCL button.

2.7.12 Diode Test

The 2kQ and 2OOkQ ranges can be used for testing semiconductor junctions as follows:

1.

Select the ohms function.

2.

Press the 2k and 2OOk button (diode symbols) in simultaneously.

3.

Display reads forward V drop of a silicon diode at 1.6mA

(l.lmA for an LED), up to 2.2V. Red terminal is positive.

Accuracy is typically better than

NOTE

r=6

mode, press the

(STO

annunciator on) and when the buffer

readings stored), the minimum and maximum

is

RCL

annunciator indicates that the maximum

(100)

have been stored.

HI

and

LO

readinas made

<I

button is held in the faster the data points scroll on

RCL

button at the desired data point and

1.5%

of reading.

B.

Release the STO/CLR button when the desired reading rate is displayed. The STO annunciator turns on and data is logged at the selected rate.

C. In the manual trigger mode (r=6), a reading is stored

every time the STO/CLR button is pressed. The follow-

ing sequence takes place after the STO/CLR button is pressed when in the manual trigger mode.

a. The Model b. The buffer location number is briefly displayed. For

example: Buffer location

c. The Model 197 displays the applied signal and waits

for the next manual trigger.

197

stores the reading.

#1

is represented by n=01.

2.8 TRMS CONSIDERATIONS

Most DMMs actually measure the average value of an input

waveform but are calibrated to read its poses no problems as long as the waveform being measured is a pure, low distortion sine wave. For complex, nonsinusodial waveforms, however, measurements made with an averaging type meter can be grossly inaccurate. Because (True Root Mean Square) measuring capabilities, the Model 197 provides accurate AC measurement for a wide variety of

AC input waveforms.

RMS

equivalent. This

of

its TRMS

2-13

2.8.1

AC

Voltage Offset

Typically, the Model on

AC

volts with the input shorted. This offset is caused by amplifier noise and offset of the TRMS converter. This offset does not affect the reading accuracy and should not be zeroed out using the

REL

197

displays

feature. Refer to Paragraph

50

counts

or

less of offset

2.7.4

step

4.

2.8.2 TRMS Measurement Comparison

The situation changes with wave.

As

before, the peak value of the waveform is the average value drops to waveform is

3.53V

A

similar situation exists

which has

Here,

(5

x

l.ll),

Other waveform comparisons can

5v,

but the average responding meter will @ve

(3.18

x

1.11>,

creating an error

an

average value of

the average responding meter gives a reading of

while the Model

the

half-wave rectified sine

3.18V.

The

of

for

the rectified square wave,

5V

and an

197

gives a

be

TRMS

found

RMS

29.4%.

RMS

lOV,

value

reading

in

Table

but

of

this

of

5V.

5.55V

of

5V.

2-7.

The RMS value of a pure sine wave is equal to peak value. The average value of such a waveform is times the peak value. Thus, for an average-responding meter, a correction factor must be designed in. This correction fac-

tor,

K,

can

be found by dividing the

average value as follows:

0.707

K

=--

BY

applying this correction factor to an averaged reading, a

typical meter can be designed to give the This works fine as long as the waveform is a Pure sine wave, but the ratios between the RMS and average values of dif-

ferent waveforms is far from constant, and can vary con-

siderably.

Table

waveforms. For reference, the first waveform is an ordinary

sine wave with a peak amplitude of

of

be seen that both meters will give the same reading, resulting

in no error in the average type meter reading.

2-7

shows a comparison of common types of

this voltage is

the

l.il

correction

6.37V,

while its RMS value

factor

0.637

-

1.11

1OV.

to

the

average reading,

0.707

times its

0.637

RMS

value

by the

RMs

equivalent.

The average value

is

7.07V.

If we

it

can

2.8.3 Crest Factor

The crest factor its RMS value. Thus, the crest factor specifies the dynamic range of a TRMS instrument. For sinusodial waveforms, the

crest factor is factor is unity.

The crest factor of other waveforms will, on the waveform in question because the ratio of peak RMS value varies. tangular pulse is related to its duty cycle; as the duty cycle decreases, the crest factor increases. The Model crest factor of TRMS measurements of rectangular waveforms with duty cycles as low as

of

a waveform

1.414.

For a symmetrical square wave, the crest

For

3,

which means the instrument gives accurate

10%.

is

the ratio

example, the crest factor

of

its peak value to

of

course, depend

197

of

a rec-

has

2.8.4 Extended F~~~~~~~~ Response

Figure

ACV

2-9

illustrates the extended

ranges

up

to

lMHz.

frequency response

of

the

to

a

2-14

-

E

1M

loot

10K

w

1

A

I

4

1K

100

10

t

I

t

~

+--

-i

-1

I

L

0

N

0

U

w

U

B

0

m

0

c

in

Waveform

Table

2-7.

Comparison of Average and TRMS Meter Readings

Ac Coupled

Peak

Value

RMS

Value

Average

Responding

Meter Reading

TRMS

Meter

Reading

Averaging

Meter

Percent Error

Half-Wave Rectified Sine

Full-Wave Rectified Sine

+

lo-

-

0

-m-

Square

+lo-:%

Rectified Square Wave

+

10-

-

1ov

1

ov

1

ov

1

ov

1

ov

7.07V

5.00V

7.07V

1o.oov

5.00V

7.07V

3.53v

7.07V

11.1ov

5.55v

7.07V

5.00V

7.07V

1o.oov

5.00V

0%

29.4%

0%

11%

1 1

7c

00

Rectangular Pulse

+1°53L

O-N

k-trlT

ll:

'DUTY

CYCLE'

Triangular Sawtooth

2-16

1

ov

1ov

5.77v

11.1V.

5.55v

q

1ov

5.77v

1.11

-

1)

3.8%

x

100%

3.1 I NTR 0 D U CTI 0 N

SECTION

3

PERFORMANCE VERIFICATION

3.3

RECOMMENDED TEST EQUIPMENT

This section contains information necessary to verify that the Model

197’s

performance is within specified accuracy. Model

197

specifications may be found at the front of this manual.

Ideally, performance verification should be performed when

the instrument is first received to ensure that no damage change in calibration has occurred during shipment. The verification procedure may also be performed whenever in-

or

strument accuracy is suspect

formance on any of the ranges with specifications, calibration should be performed as

described in Section

If

the instrument does not meet specifications

and

it months since date of shipment), contact your Keithley representative mine the action to be taken.

3.2

E

N

V I R

0 N M

All measurements should be made at an ambient temperature between humidity less than

18°C

5.

is still under warranty (less than

E

NTA L C 0 N D IT

and

28°C (65°F

80

%

.

following calibration. If per-

or

functions is inconsistent

NOTE

or

the factory to deter-

I0

N

S

to

82°F)

with a relative

or

12

Equipment for verifying the performance of the Model listed in Table 3-1. Alternate equipment may be used as long

as equipment accuracy is at least equal to the specifications listed in Table 3-1.

3.4

INITIAL CONDITIONS

Before performing the verification procedures, make sure the

Model

1.

2.

3.5

The following paragraphs give the basic verification procedure for the following functions resistance and current

197

meets the following conditions:

If

the instrument has been subjected to temperature below

18°C (65°F)

the instrument to reach temperatures within the range. Generally,

10°C

is

Turn on the Model hour. The instrument may be operated from either line

power of battery pack power, as long as the battery pack has been fully charged as described in paragraph

VERl FICATION PROCED U

or

above

28°C (82”F),

it

takes one hour to stabilize an instrument that

(18°F) outside of this range.

197

and allow

allow sufficient time for

it

to warm up

RE

DC

volts, AC volts,

197

for

2.3.3.

one

is

I

Mfg

Fluke Fluke

Valhalla

Fluke

I

Model I Description

343A 5200A 2500E

5450A

521 5A

DC Voltage Calibrator AC Voltage Calibrator AC-DC Current Calibrator

Resistance Calibrator

Power Amplifier

Table

3-1.

Equipment Specifications

I

Specifications

200mV, 2V, 20V, 200V, 1 OOOV ranges 200mV, 2V, 20V, 1 OOV 50Hz 200pA, 2mA, 20mA, 200mA, 2000rnA, 1 OA ranges

50.03% DC,

I

OOR,

1

range

+O.O1°/o;

&0.5%

1

OOOV range: 1 OHz-30Hz

-tO.IO%;

max

@

=.

+0.1%

ka,

1

OkR, 1 OOkn

10MQ

1

OOV max

13kHz

=

f0.005%

to

1 OkHz

+0.05%

AC to 5kHz (at full scale)

ranges

range 50.05°/o;

k0.12%;

@I

1

OOkHz = 10’VHz; 750V

1

07VHz

+0.005%; 1 MR

1

OOMQ

50kHz-l OOkHz

3-1

-

.,?

WARNING The following procedures require that high voltages may be applied to the input ter-

minals of the Model 197. Use normal safety precautions to avoid possible electrical shock which could result in personal injury or death.

3.5.1

DC

Voltage

1.

Select the

2. Connect the calibrator to the instrument as shown in Figure

3. Set the calibrator to Leave the relative mode enabled for all DCV

measurements. Check to see that the reading is 000.OOOV

+1

4.

Apply a positive 200mV to the minals. The reading must be within the limits specified in Table 3-2.

5. For each remaining range, apply the required voltage as specified in Table 3-2 and verify that the reading is within specifications.

6.

Repeat all checks with negative voltage.

DC

Do not exceed IOOOV between the input HI

and

LO

terminals or damage to the instru-

ment may occur.

3-1.

count.

Accuracy Check

volt function and autorange.

CAUTION

OV

and enable the relative mode.

HI

and

LO

INPUT

ter-

Table 3-2. Limits for DC Voltage Verification

197

DCV Range

200mV

2v

20

v

200

v

1000

v

*The limits shown do not include test equipment

tolerances.

3.5.2

AC

Voltage

Do not exceed 750V RMS, IOOOV peak 107VHz between HI and minals or instrument damage may occur.

1.

Select the AC volts function and autorange. Do not use

REL

to zero the offset in this procedure. Refer to paragraph

2.7.4 step

2. Connect the AC calibrator to the HI and minals of the Model 197 as shown in Figure 3-2.

3.

Set the calibrator to output 2.OOOOOV at a frequency of 50Hz. Verify that the reading is within the limits specified in Table

4.

Repeat the 2.OOOOOV AC measurement at the other frequencies specified in Table 3-3.

5. Check the 2OV, 2OOV and 750V ranges by applying the required voltage and frequencies specified in Table verifying that the readings are within the specified limits.

3-3.

Applied

DC Voltage

200.000mV

2.00000

20.0000

200.000

1000.00

4.

Allowable Readings*

(18OC to 28OC)

199.965

v v

1.99976

19.9968

199.968

999.68

Accuracy Check

CA UTlO N

LO

INPUT ter-

to

200.035

to

2.00024

to

20.0032

to

200.032

to

1000.32

LO

INPUT ter-

3-3

and

I

MODEL 197

Figure 3-1. Connections for DCV Verification

3-2

I

HI

AC

CALIBRATOR

MODEL 5200A

and

10

MODEL 197

MODEL 5215A

Figure 3-2. Connections for ACV Verification

Table

3-3.

Limits for

AC

Voltage Verification

197 AC

Range

200rnV

2v

20

200

750 V

3.5.3

Resistance Accuracy Check

Resistance verification is performed by connecting known, precise resistance values to the checking to see that the displayed reading is within the required limits. Measurements on the ranges will be done using the 4-terminal configuration to minimize errors due to the voltage drop across the test leads.

Do not exceed 450VDC

seconds per minute, 350V rms continuous

between the HI and

the instrument might be damaged.

1.

Select the ohms function (AC/DC button must be out) and

the

2003

range.

2. Use Kelvin test leads (e.g. Keithley Model put

HI

and

LO,

and then

minals. Short the leads together. Enable the relative (REL)

mode. Check to see that the display reads

the relative mode enabled for the remaining resistance measurements.

3.

Connect

3-3.

measurement.

4.

Check to see that the displayed reading is within the limits specified in Table

a

1903

calibration resistor as shown in Figure

Note that the 4-terminal configuration is

Applied

AC Voltage

200.000rnV

2.00000v

20.0000v

v

200.000v

v

7 50. OOOV

HI

CAUTlO

LO

OHMS

3-4.

20Hz

197.900

to

202.100

1.97900

to

2.02100

19.7900

to

20.2100

197.900

to

202.100

739.63

to

760.37

and

LO

input terminals and

2OOQ,

2kQ

and 2Okn

N

or

peak AC

INPUT terminals or

SENSE

for

10

1641)

in the in-

HI

and

000.000.

used

50Hz

199.200

to

200.800

1.99200

to

2.00800

19.9200

to

20.0800

199.200

to

200.800

743.37

to

755.62

LO

ter-

Leave

for this

10kHz

198.600

to

201.400

1.98600

to

2.01400

19.98600

to

20.1400

199.860

to

201.400

740.50

to

759.50

5.

Connect shown in Figure range. Verify that the displayed reading is within the limits specified in Table

6.

Connect a 19kO calibration resistor to the instrument as shown in Figure 3-3. Switch the instrument to the 20k3 range. Verify that the displayed reading is within the limits specified in Table 3-4.

7.

Connect a 190kn calibration resistor to the instrument as shown in Figure 3-4. Switch the instrument to the 200k3 range. Verify that the displayed reading is within the limits specified in Table 3-4. Note that the 2-terminal configuration may be used on the 2OOkn and higher ranges.

8.

Continue with each of the calibration resistance values listed in Table 3-4. Be sure to place the Model correct range for each measurement. The remaining readings may be done using 2-terminal configuration.

Table

197 Range

;j:

3-4.

200

20M

200M

2OkHz

196.750

to

203.250

1.96750

to

2.03250

19.6750

to

20.3250

196.750

to

203.250

a

1.9kn

50kHz

189.600

to

210.400

1.93600

to

2.06400

19.3600

to

20.6400

193.600

to

206.400

calibration resistor

3-3.

Switch the instrument to the

100kHz

189.600

to

210.400

1.93600

to

2.06400

19.3600

to

20.6400

to

the

3-4.

Limits for Resistance Verification

k

Applied

Resistance

190.000

1.90000

19.0000

190.000

1.9OOOOMfl

19.0000Mn

190.000Mn

kQ

k!J

kQ

Allowable Readings

I

(18OC to 28OC)

n

189.959

1.89964

18.9949

189.949

1.89931

18.9770

186.199

to

instrument

197

on the

190.041

1 .go036

19.0051

190.051

1.90069

19.0230

193.801

as

2kfl

3-3

Figure

3-3.

Connections for

Verification (4-ter m i nail

HI

200,2k

1,

and

20k

CALIBRATION

RESISTANCE

(MODEL 5450A)

Range

I

1.

Select the

2. Connect the instrument to the DC current calibrator as shown in Figure should be connected to the HI terminal and the the calibrator output should be connected to

3.

Set the calibrator mode.

4.

Verify that the displayed reading is within the limits specified in Table

5.

Switch the Model 197 calibrator to output +20.0000mA. Verify that the displayed reading is within the limits specified in Table

DC

current function. Select the

3-5.

The HI side of the

to

00.000

and enable the realtive

3-5.

to

the 20mA range. Set the

20OOmA

AMPS

LO

LO.

range.

terminal

side of

(REL)

3-5.

6.

Switch the Model 197 to the 200mA range. Set the calibrator to output +200.000mA. Verify that the displayed reading is within the limits specified in Table

3-5.

7.

Switch the Model 197 to the 2000mA range. Set the

calibrator output

within the limits specified in Table

8.

Set the Model 197 rent to the 10A and

Be sure to connect the calibrator

LO

terminals. Otherwise, applying the specified in Table panel current fuse.

+

2000.00mA. Verify that the reading is

3-5.

to

the 10A range. Connect the DC cur-

LO

terminal as shown in Figure

NOTE

to

the 10A and

5A

(as

3-5)

would blow the front

3-6.

Figure

3-4.

Connections for

200k

through

MQ

Ranges Verification (ZTerminal)

3.5.4

DC Current Accuracy Check

DC current accuracy is checked by connecting a calibrated

DC

current source to the to 2000mA (10A and 10A). The accuracy is then verified by referring to Table which shows the exact number of counts allowable in order to remain in the limit of the specifications.

Do

not exceed 2A to the

terminals or the front panel amps fuse will

blow.

Refer to paragraph 2.4.4.

HI

and

LO

INPUT

LO

terminals for 2000mA through

CAUTlO N

HI

terminals for up

and

LO

INPUT

3-5

9. Apply

5.0000A.

specified in Table

10.

Repeat steps 1 through 10 with negative current.

Table

197

+0.50000VDC

Verify that the reading

3-5.

DC Range

200 pA

2mA

20rnA

200rnA

2000mA

10 A

to the current calibrator to output

is

within the limits

3-5.

Limits for DC Current Verification

Applied

DC Current

200.000pA

2.00000rnA

20.0000rnA

200.000rnA

2000.00rnA

5.0000 A

Allowable Readings

(18OC

199.785

1.99785

19.9785

199.585

1995.85

4.9610

to

29OCI

to

200.215

to

2.00215

to

20.0215

to

200.415

to

2004.15

to

5.0390

3-4

3.5.5

AC Current Accuracy Check

0

“10

f

INPUT

LO

\

LO OUTPUT

0)

I

MODEL

197

MODEL 343A MODEL 2500E

Figure

~~ ~~ ~

3-5.

Connections for DC Current Verification

INPUT

DC VOLTAGE CURRENT

CALIBRATOR CALIBRATOR

INPUT

MODEL 343A MODEL 2500E

(200pA

HIOUTPUT

to

2000mA)

AC

current accuracy is checked by connecting a calibrated

AC current source to the

200pA to 2000mA, 10A and 20A, and then verifying that the displayed reading is within

the specified range.

Do

not exceed 2A between the INPUT terminals or instrument damage might occur. Refer to paragraph

Select the AC current function on the Model 197. Place

1.

the instrument in the 2000mA range. Connect the AC calibrator to the Model 197 as shown in

2. Figure 3-7. Set the calibrator frequency to

use the relative mode to zero the offset in the AC mode.

Set the calibrator to output 200.000pA and switch the

3.

Model 197 to the 200pA range. Verify that the displayed reading is within the limits specified in Table

4.

Change the Model 197 to the 2mA range. Set the calibrator to output 2.00000mA. Verify that the displayed reading is within the limits specified in Table

Change the Model 197 to the 20mA range. Set the

5.

calibrator to output 20.0000mA. Verify that the displayed reading is within the limits specified in Table

Change the Model 197 to the 200mA range. Set the

6.

calibrator to output 200.000mA. Verify that the displayed reading is within the limits specified in Table

Change the Model 197 to the 2000mA range. Set the

7. to

calibrator

reading is within the limits specified in Table Connect the calibrator to the Model 197

8.

minals as shown in Figure

the 10A range.

Be sure to connect the calibrator to the 10A and

LO

specified in Table panel current fuse.

output 2000.00mA. Verify that the displayed

terminals. Otherwise, applying the 5A (as

HI

and

LO

INPUT terminals for

LO

terminals

CAUTION

3-8.

Change the Model 197 to

NOTE

3-6)

would blow the front

for

HI

and

2.4.4.

IkHz.

IOA

2000mA

LO

Do

3-6.

and

LO

not

ter-

to

Figure

3-6.

Connections for DC Current

Verification

(2000mA

to

20A)

Set the calibrator to output 5.0000A. Verify that the

9.

displayed reading is within the limits specified in Table

3-6.

3-5

Table

3-6.

Limits for AC Current Verification

197

AC Range

200 pA

20rnA

200rnA

2000rnA

10

*Not

to

2rnA

A

exceed

Applied

AC Current

200.000pA

2.00000rnA

20.0000rnA

200.000rnA

2000rnA

5.0000 A

1

kHz.

20Hz

197.900

to

202.100

1.97900

to

2.02100

19.7900

to

20.2100

197.900

to

202.100

1979.00

to

2021

.oo

4.9150

to

5.0850

50Hz

198.300

to

201.700

1.98300

to

2.01700

19.8300

to

20.1700

198.300

to

201.700

1983.00

to

2017.00

4.9400

to

5.0600

5kHZ

195.750

to

204.250

1.95750

to

2.04250

19.5750

to

20.4250

198.270

to

201.730

1982.70

to

2017.30

4.9400"

to

5.0600

I

,

MODEL 197

INPUT

AC VOLTAGE CUR RENT

CALIBRATOR CALIBRATOR

INPUT

MODEL 5200A MODEL 2500E

Figure

3-7.

Connections for AC Current Verification (200pA to 2000mA)

I

0

-

Figure

f

o\

INPUT

LO

MODEL 197

-

HI

INPUT

AC VOLTAGE CALI BRATOR CALIBRATOR

MODEL 343A

~~

3-8.

Connections for AC Current

LO

~~ ~

Verification (2000mA to 10A)

LO OUTPUT

HI

OUTPUT

CURRENT

MODEL 2500E

-

~

3-6

SECTION

4

THEORY

4.1 INTRODUCTION

This section contains an overall functional description of the Model 197. Information pertaining to the Model 1978 Battery Pack option is also included. Detailed schematics and component layout drawings are located at the end of this instruction manual.

4.2 OVERALL FUNCTIONAL DESCRIPTION

The Model 197 is a voltage ranges, seven resistance ranges and six current ranges. A simplified block diagram of the Model 197 is shown in Figure 4-1. The heart of the Model 197 is the A/D The Model 197 voltage and current measurements are based converter that translates the conditioned analog input signal on comparing the unknown signal with an internal 2V into a form usable by the microcomputer. reference voltage. During each measurement cycle the

5%

digit DMM with five AC and DC

AC

OF

and DC

OPERATION

4.3.2 Input Buffer Amplifier

The input buffer amplifier provides the necessary isolation between the input signal and the A/D converter. The amplifier is a noninverting, low noise, high impedance circuit

X1

or

with microprocessor and is range and function dependent. Figure 4-3 shows the simplified schematic of the input buffer amplifier. The gain is XI0 when Qll6 is ON and Q116 is

4.3.3 2v Reference Source

unknown is sampled along with a zero measurement and a reference measurement to compute the unknown voltage.

XI0 gain. The amplifier gain is controlled by the

X1

OFF.

when

2V

4.3 ANALOG CIRCUITRY

The following paragraphs contain a description of the input multiplexer, buffer amplifier, +2V reference and A/D con-

verter

diagram number 197-106 located at the end of this manual.

circuits.

These circuits

may

be found

on

schematic

4.3.1 Multiplexer

The multiplexer connects one of four signals to the buffer amplifier: signal, zero, reference and ohms reference. The multiplexer, shown in Figure 4-2, is made up of 4 JFETs which are controlled by the microprocessor through U114. The FETs are driven by drivers U103 and U112. The drivers convert the digital signals of the microprocessor to signals usable by the FETs.

FET

Note that the particular

range dependent. This is done manner that eliminates the errors due to the

It

Q106 and Ql09.

of

u102.

Ordinarily, FET switching creates transients which could be seen in the final measurement. These effects are minimized in the Model 197 through the use of software generated delays

also reduces errors due to leakage current

used to sense zero on DCV is

so

that zero may be sensed in a

ON

resistances of

-

The 2V reference is made up of a highly stable Zener diode

(VRl03), an op-amp and a resistive divider. U109 and R125C,

E

D, and Zener voltage variations. R121D,

divide

The output of U109 is buffered by Q122 to form a Ply.

act as a constant CWTent Source to minimize the

E

and

F

is

then used to

down

the

6.4v

to

2v.

+1OV

sup-

4.3.4 Input Signal Conditioning

For DCV and ACV the signal conditioning is performed by R103, R104, R105 and their shunt capacitors. Range switching is performed by K101, K102, K103, Q105, Q106 and

QlO8

Ql09. Q107 and eliminates the errors due to the on resistances of Q106 and Ql09. The FETs are driven by U112.

The following attenuation is provided:

+I

is used on the 200mV and 2V ranges.

+lo

is used on the 2OV range.

+loo

is used on the 2OOV range.

+lo00 is used on the 1000V/750V range.

are used to sense zero in a manner that

4-

1

>

i-!

4-2

OVS~SNAL/R REF

HI

,

.

and R113. R106 and R107 are used exclusively on the 200mV

DCV

and 2V ranges of R113 is used exclusively on the 200mV and 2V ranges of ACV

to limit current to CR102 and CR104.

to limit current to Q114 and Qll5.

R

REF

LO

(VZERO

ON

and

VREF~R

ZOVDC,

lOOOVDC RANGES)

SENSE

Figure

HI

4-2.

FROM FET DRIVER

Q110

1

I

FROM FET DRIVER

0113

1

I

f

-

FROM FET DRIVER

JFET

Multiplexer

+

IUTPUT TO

BUFFER

AMPLIFIER

Signal conditioning for current is performed by R112, R118 and R123 current shunts. For DC current measurements the shunt voltage drop (220mV full range) is applied directly to

the input signal FET for conversion. In AC current, the shunt

voltage drop is treated as a <220mV

ed to the AC converter section. Overload clamping occurs at

3

diode drops which

crest factor current waveforms.

In DCV the properly scaled signal is applied directly to

through R106, R107 and C109. In ACV the scaled signal is ap-

plied to the

that is applied to

Resistance measurements are made using the ratiometric technique (see Figure selected, a series circuit is formed between the ohms source, a reference resistor, and the external unknown resistance. An ohms source of 4.3V is obtained by placing a protection diode (CR101) in series with a work. A current then flows through the reference resistor and the unknown resistance. Since this current is common to both resistances, the value of the unknown resistance can be calculated by measuring the voltage across the reference resistor and the voltage across the unknown resistance.

AC

is

a level high enough to permit high

converter for transformation to a DC signal

4111.

4-4).

When the resistance function is

+5V

AC

signal and is switch-

Ql11

supply and the ratiometric net-

INPU? FROM

MULTIPLEXER

Figure

Protection for the AC and by Q103, Q127, Q114,

200kR

4-3.

Simplified Schematic of the Input Buffer Amplifier

Qll5,

GAIN

SELECT

DC

voltage functions

CR102, CR104, R106, R107

is

provided

<

The following ohms reference resistors are used (see Figure

4-5).

(1kR)

R103llR105AllR105B R105DllR105AllR105B R105CllR105AllR105B (100kR) on 200kR range R105AllR105B (1MQ) on 2MR range R105A (10MQ) on 20Mfl and 200MR ranges

By measuring the four inputs to the A/D converter the unknown resistance can be computed by the microprocessor using this equation:

RREF

Rx

=

Vfl

For the 200fl range VR SENSE tually multiplied by a factor of

on 200R and 2kR ranges

(lokfl)

(VR

SENSE HI

REF HI

on 20kR range

-

VQ

HI

and

10

in the buffer circuit.

VQ

REF

VR

SENSE

LO

SENSE

LO)

LO

are ac-

4-3

FRONTPANEL

CONN.

R1

m2:

-1

4

TERM'

,I

.-,I

"

I

IR2;

:

current through

I

1

I

1

I

RREF

I

I I

10

I

VI1

I

10

'

VR

I

10

I

REF

Vfl

HI

LO

through is much closer to the actual value across the measured resistance, minimizing the error.

4.3.5

The Model 197 uses a combination constant frequency

variable pulse width, charge balance, single slope analog-to-

digital converter.

the Model 197

R1

A/D

R2

and

R3

is much smaller than the current

and R4. Thus, the voltage seen by the instrument

Converter

A

simplified schematic of the AID used in

is

shown in Figure 4-4 with an associated waveform. Refer to schematic 197-106 for detailed component location.

RX

I

=

I1

I

RREF

(VR

SENSE

HI

-

VR

REF

HI

-

Vfl

REF LO

Figure 4-4. Input Configuration During

SENSE

I

SENSE

I

LO)

2-

and

Vfl

LO

4-Terminal Resistance Measurements

Protection on the ohms ranges is accomplished by RT101,

QlOl

and Q102. For an input voltage applied to the 3 input terminals, resistors to a safe limit. RT101 limits the current to Q102. R105A provides protection of the ohms source by limiting current.

The Model 197 is equipped to make 2resistance measurements. Generally, 4-terminal measurements should be made on the 2003 range because the

relatively large output current can develop a significant voltage across the test leads, affecting instrument accuracy.

Figure 4-4 shows the equivalent circuit of the input circuit. Ry

is the unknown measured resistance and R1, represent the test lead resistance. R2 and ly during 4-terminal measurements. When using a 2-terminal configuration, all the current flows through the test leads and R4. developed across the test leads can be significant. Since the voltage is sensed across the combined resistance of and To use a 4-terminal connection, a second set of leads R3) are connected to the unknown resistance. The amount of

QlOl

and Q102 clamp the voltage to the reference

QlOl

or

4-terminal

R2,

R3

are connected on-

If

Rx

has a low value, the amount of voltage

R,;

considerable error can be introduced into the reading.

and

and R4

R1

Rl,

Rx

(R2

and

The charge balance phase begins when the input enable/disable line is set high. This occurs at the end software-generated delay period that allows the signal tle after the appropriate multiplexer

FET

is turned on.

to

of

set-

Once this occurs, an offset is added to the signal from the buffer to convert

it

to a negative unipolar input to the integrator.

The signal from the buffer has a range of -2.2V to +2.2V on

OV

the volts and amps functions, and function. Therefore, it is necessary

the ohms function. This is done by switching

The integrator (comprised of 4121, UllO and

up until

it

just passes the charge-balance comparator

to +4V on the ohms

to

have a larger offset

in

R117B.

C123)

on

ramps

threshold voltage. When the rising edge of Q3 (U119) occur

of U11LA goes high forcing

Q1

The time of comparator

amount of

of U117A remains high depends upon the state

U108B

I,,

fed back to the integrator input will be propor-

when Q3 (U119) goes high. Thus, the

IcB

into the integrator input.

tional to the input voltage. Each time the output U117A goes

it

high

is gated (inside the microprocessor) with the microprocessor's internal clock and pulses are counted. Once U117A goes low the process repeats itself.

The charge balance phase continues for 100msec. At the end of the charge balance phase, the output of the integrator is resting at some positive voltage. Since the integrator output is connected to the noninverting input of the U108A, its output will stay high until the intergrator ramps negative. During single slope Q120 is turned off and R129 is connected to

+5V. The single slope comparator is then gated with the microprocessor's internal clock and counted. Once the comparator output goes low the microprocessor stops counting and can compute the reading.

a

4-4

4.3V OHMS SOURCE

i

Q105

-

HI

INPUT

0

SENSE

i-

->

RX

Q

i

::I-

..-

4.3.6

AC Converter

On the a

accurate voltage measurements at higher frequencies and lower input levels. On all other ranges a gain of processor. The output of verter chip, corresponding signal

4.4

200mV AC

X5

voltage amplification. The gain stage

X1.

FET.

range the input is routed through

The gain

U106,

DC

of

U104

which converts the level. The

DIGITAL CIRCUITRY

-

SENSE LO

Figure

U104

is controlled by the micro-

is applied to the TRMS con-

DC

output is then applied to the

HI

->TO

4-5.

Resistance Measurement Simplified Circuit

is

used to permit

U104

is configured for

AC

input signal to the

Q106

-

3

TO Q113

MULTIPLEXER

Q112 OF

MULTIPLEXER

U104

for

a109

K103

1

-

.'

A

12

REF

LO

'TO Q110 MULTIPLEXER

OF

4.4.1

Microcomputer

The microcomputer centers around the microprocessor. dressing

Timing of the microprocessor is accomplished by the use of

Y101; a 3.2768MHz

ed down by 5 to obtain a bus operating frequency

655.36kHz.

6)

through the binary divider

of

and supplies timing to all other parts of the instrument

It

is an 8 bit microprocessor with direct ad-

up to

8k

bytes on a shared address and data bus.

crystal. Internally this frequency is divid-

This is present on the address strobe of

U119.

OF

146805E2 CMOS

U124

of

(pin

Model puter. This section briefly describes the operation of the various sections of the microcomputer and associated digital circuitry. For more complete circuit details refer to schematic diagram number

197

operation is controlled by the internal microcom-

197-106

at the end of this manual.

The software for the porary storage is provided by calibration constants on power up and as microprocessor's in-house functions. for the data logger. the calibration constants.

MPU

U113

is stored in

U121. U121

is the

NVRAM

U122 (PROM).

is used to share the

It

also stores readings

and is used

RAM

Tem-

for the

to

store

4-5

SINGLE SLOPE

ENABLE/DISABLE

-

BUFFER

V

A

fl

R117C

R117B

n

R128

+

CHARGE BALANCE

5v

A

INPUT

ENABLE/

DISABLE

Figure

4.4.2 Address Decoding

U123 is used to latch in the address that is on the bus when the

address strobe of U124 goes high and presents (U122) during data strobe.

it

to the PROM

4-6.

SINGLE SLOPE

TO

1rP

COMPARATOR

CLOCK

A/D

Converter

The display board also houses the special function keys: dB, REL, STO/CLR and RCL.

U118B U117A

1

4.5 DIGITAL CALIBRATION

4.4.3 PIA

u114 provides for most of the control of the instrument. controls all ranging hardware, A/D converter, and data output and input for the

IEEE

option.

4.4.4 Display Board

The LCD display is driven by a flat pack LCD controller chip

it

U201 and control lines. During power-up the microprocessor configures U201 to drive the triplexed display.

In order to drive the display correctly four voltages are obtained from R134. The clock required by U201 is obtained from

U119.

4-6

communicates to the microprocessor through

The Model 197 uses digital calibration tiometers in the instrument to facilitate calibration. The constants that the Model 197 uses are stored in a nonvolatile electrically alterable read only memory (U113), and are read on power-up of the instrument. There is one constant for each

It

range on DCV, ACV and which uses the constant from the 2V range. ACA functions the 200mV DC and 200mV AC constants are used respectively.

0,

except for the 750VAC range

to

eliminate all poten-

On

the DCA and

4.6 POWER SUPPLY

4

Fuse F102 is the LINE FUSE which is internally accessible. SlOl is the power on/off switch and S102 selects 230V operations by placing the transformer primary windings in parallel

or

series.

115V

or

T101,

the power transformer has two secondary windings;

197

one for the Model Analog Output/IEEE option or the Model The bridge rectifier for both the plus and minus supplies.

the

15V

Zener

(VR104)

charging.

R132

pre-regulator to the

4.7

Maximum battery charging rate is achieved when the instrument is connected to line power and the on/off switch is off. Fullwave rectified voltage from

VR104

limits current to the

MODEL

acts as a pre-regulator to the

1978

and the other for the Model

1973

(cRl07)

-9V

functions as a fullwave rectifier

R131

and to the batteries

15v

Zener

VR105. VR105

supply.

BAlTERY

OPTION

CR107

is

applied to

IEEE

limits current to

(if

installed) for

+

1OV

1972

option.

supply.

acts as a

R102

and

BTlOl

the charging current rises above 150mA. The batteries are of the quick recharge type and will charge in the instrument turned on the batteries will trickle charge at approximately 40mA.

With

generated using a

of

Low battery detection is accomplished by the comparator

(U102)

across level for the comparator is set by

to

charge the batteries.

the battery pack installed, the negative supply is

CMOS

the inverter is applied to

and the microprocessor. A voltage level of

BTlOl

signals and end of useful battery life. The trip

QlOl

acts as a current sink

voltage inverter

CRlOl

and

R103

8

to

(UlOl).

C101

and

R104.

10

hours.

The output

for filtering.

With

11.6V

if

SECTION

5

MAINTENANCE

5.1

INTRODUCTION

This section contains installation, service and calibration information for the Model ment, line voltage selection and troubleshooting procedures are also included in this section.

The procedures described

are intended for use by qualified service personnel only. Do not perform these procedures unless qualified to do the steps covered in this section expose the individual to potentially lethal voltages that could result in personal injury or death if

normal safety precautions are not ob-

served.

5.2

TOP COVER REMOVAL/INSTALLATION

The top cover of the Model service the unit

the Model

follows:

Disconnect the line cord and all other equipment from the Model 197 before removing the top cover.

1973

or

install the Model

or

Model

197

and Model

WARN I NG

197

must be removed in order to

1972 IEEE-488

WARN I NG

1978.

Fuse replace-

in this section

so.

Many of

1978

battery pack and/or

interface. Proceed as

WARNING

Disconnect the line cord and remove all test

leads from the terminals of the Model 197.

1.

Remove the top cover as explained in paragraph

2.

Remove the shield.

A.

Remove the screw that secures the shield to the mother board. The screw is located at the rear of the shield.

B.

Carefully pull up on either side of the shield.

Lift

C.

3.

Position the battery board as shown in Figure secure

screws are positioned through the shield into the battery

board fasteners.

4.

Place the battery pack in the bracket and position on the shield as shown. Route the two screws through the shield into the bracket and tighten.

5.

the shield out of the Model

it

to the shield using the two supplied screws. The

CAUTION

Do not allow the batterv leads to short together or damage to the batteries may occur.

Connect the red battery lead to the +RED terminal pin on the battery board. Connect the black battery lead to the

-BLK terminal pin on the battery board.

CAUTION Be careful not to reverse the wires (NOTE: Red to Red and Black to Black).

197.

5.2.

5-1

and

1.

Turn off the powerr disconnect the line cord and remove all

test leads from the terminals of the Model

2.

Turn the unit over and remove the four screws from the bottom of the case.

3.

Turn the unit over again and separate the top cover from

the rest of the unit.

4.

To reinstall the top cover, position the

to the bottom cover; replace top cover and screws.

5.3

BATTERY PACK (Model

1978)

197.

tilt

bail properly in-

INSTALLATION

Refer to Figure stall the battery pack:

5-1

and perform the following procedure to in-

6.

Carefully Model

~~~l~~~

7.

Connect the ribbon cable from the battery board to on the mother board. Make sure pin 1 on the cable connects to pin Figure

place

the

shield (with battery pack) back

197

so

that

it

seals properly on the

retaining

The retaining screw on the rear

serves to connect the shield to circuit

5-1.

1

of

Screw

P1009.

in

the shield,

NOTE

of

the shield also

Refer to the detailed drawing of

LO.

two

into

spacers.

the

__I

P1009

5-1

CAUTION Make a close visual inspection of the connections to ensure that they are properly

connected. Otherwise, damage to the instrument may result.

IEEE

board is secured to the mother board by a support

post at the rear and connector

it

board up until

disengages from the connector and sup-

P1008.

To remove,

port post.

3.

Replace the blown fuse with the following type:

1/8A, 250V, 3AG,

Slo-Blo

(Keithley Part Number FU-20)

lift

the

8.

Reinstall the top cover

The

IEEE

Interface options do not run off of bat-

as

explained in paragraph 5.2.

NOTE

tery power.

5.4

LINE VOLTAGE SELECTION

The Model 197 may be operated from either 105v-125V or 210v-250v, 50-60Hz. A special transformer may be installed for 90-llOv or 195-235V operation. The instrument was shipped from the factory set for an operating voltage marked on

as

the rear panel. To change the line voltage, proceed

1.

Turn off the Model 197 and disconnect

it

from line power.

follows:

2. Set the LINE VOLTAGE switch on the back of the instrument to correspond to line voltage available. Example: 11OVAC is available, set the switch to 105V-125v.

CAUTION Connect only to the line voltage selected. Application of incorrect voltage can damage the instrument.

CAUTl 0 N

Do

not use a fuse

specified or instrument damage may occur.

If

the instrument persistently blows the fuse, a problem may exist within the instrument. before operation may continue.

4.

If

the IEEE interface was installed, reinstall the interface as

If

so,

with

a higher rating than

the problem must be corrected

follows:

Install the rear standoffs.

A.

Position the interface board above the rear standoffs.

B.

WARNING

Do

not push down on nector pins may cause personal injury.

Guide the terminals of

C.

that end Push down on the other side of the interface board

D.

it

snaps onto the rear most standoff. Make sure

will

of

the board to mate the connectors.

J1008.

pass through

P1008

The male con-

and firmly push down on

J1008

board is properly seated on the other two standoffs. Reinstall the modified top cover.

E.

5.

Reinstall the top cover

as

explained in paragraph

and

until

the

5.2.

3.

Plug the power cord into a properly grounded outlet.

WARNING

Ground the instrument through a properly

grounded receptacle before operation.

Failure to ground the instrument can result in severe injury or death short circuit or malfunction.

5.5

FUSE REPLACEMENT

5.5.1

Line Fuse Replacement

in

the event of a

The line fuse is located internally in the Model 197. For exact fuse location refer to Figure 5-1. To replace the fuse proceed as follows:

1.

Remove the top cover as explained in paragraph 5.2.

2.

If

the Model 1973 or Model 1972 IEEE-488 interface is in-

stalled, it must be removed to gain access to the fuse. The

.

___

-

-__-~

5-2

5.5.2

Current Fuse Replacement

The current fuse protects the 200pA through 2000mA ranges from an input current greater than 2A. To replace the current fuse, perform the following steps:

Turn off the power, disconnect the power line and remove the test leads.

Place the end of a flat blade screwdriver into the slot of the fuse holder on the front panel. Carfeully press in and rotate

the fuse carrier one-quarter turn counterclockwise. Release

pressure, remove the fuse and the fuse carrier from the

front panel. Remove the defective fuse and replace

it

with the following type: 2A, 250V, 3AG, normal blow (Keithley Part Number FU-13) or equivalent

CAUTION

Use

only

the recommended fuse type. If a fuse with a higher current rating is installed, instrument damage may occur upon overload.

TOP

COVER

175313

,

'REAR PANEL LABEl

MC

372

'CURRENT FUSE

HOLDER BODY

FH

21

'CURRENT

FUSE

CARRIER

FH

25

I

~

I

1

I

Figure

5-1.

Model

197

Miscellaneous Parts

5-3

+

5.6 FRONT PANEL CALIBRATION

Calibration should

the perforiiiaiice verific,ition procedurch in Section sliow that the the calibration procedures in this section cannot be formed tion in this section. Keithley representative or the

ini

If

rear your instrument. When this switch is in ENABLED, loi\~

NVI<

properly, refer to the troubleshontiiig iiiforma-

t i m.

vou

have

revision C level softivxe in your

pinel

external calibration snTitcli has

you

to

AM.

For

Re\kion

the iactory for calibration informcition. Refer

to

pxagrapli

sion lei~l.

be

bIodel

performed

197

is out

everv

12

of

specifkcition.

months, or

If

my

per-

If

the problem persists, contact your

f'ictory

pc~riiiaiiciitly store idibration constants in

NOTE

A

or

Revision B software contact

5.7.2

to determine sofhvare revi-

for further infor-

Model

been

197,

added to

it

if

3

of

al-

a

5.6.2

5.6.3

Environmental Conditions

Calibration Switch

5.6.1

Ccilibratioii may listed in Table

be

uscd

good

Recommended Calibration

Eq

u

5-1.

as

long

as

the syccificatioiis listed in Table

Description

DC

Voltage Calibrator

AC Voltage Calibrator

Resistance Calibrator

i pmen

as

t

be

performed using

Alternate calibration equipmeiit ii~ay

the equipment's accuracy is at

Table

the

ecpipment

least

3-1.

5-1.

Recommended Calibration Equipment

Required Minimum Specifications

200mV, 2v, 2OV, 200V,

1

(90 day accuracy)

200mV, 2V, 20V, 200V and 750V ranges, +0.05%

190R

1.9k12 19k

190k

1.9MR

19M

(90 day accuracy)

0.003"%

O.OO3"%

0.003"

OOOV,

,

12,

(2,

12,

0.003"%

+

Yo + 0.5pV

0.003'

50ppm

,

1

OOpprn

500ppm

%,

as

+

0.5LiV

+

0.5LtV

+

0.5pV

0.5~1v

WARNING

Some procedures require the use

voltage. Take care to prevent contact with

live circuits which could cause electrical

shock resulting in injury or death.

Mfr.

Fluke

Model

5440

5200A 5450A

No.

&

521

of

5A

high

5-4

+

NOTE

Calibration may be stopped at any time and if desired, only selected ranges may be calibrated.

5-2

FIGURE

WAS DELETED

ON

DC

VOLTAGE

CALIBRATOR

5440

MODEL

REVISION

C

OF

THIS

Figure

MANUAL.

5-2.

5.6.4 DC Voltage Calibration

Select the DCV function. Connect the DC calibrator to the Model

1.

2.

3.

4.

5. Select the next range (2V) and set the calibrator output to

6.

7. Reverse the calibrator leads in order to output -1.90000V.

8.

9. Repeat steps

197

as shown

The following procedure must be performed in

the exact sequence listed.

Press the message "CAL" is displayed. Release the buttons. The Model 197

mode is indicated by the "C" annunciator on the front

panel display.

Select the 200mV range short INPUT

the

Set the calibrator to output +190.000mV.

Adjust the display to read 190.000 with the use of the

STO/CLR and RCL buttons. The STO/CLR button in-

crements the displayed reading. The RCL button

decrements the displayed reading. The longer either button is held in, the faster the displayed reading is modified.

f

1.90000v.

Repeat step 4 to read 1.90000.

Repeat step 4 to read -1.90000.

ranges listed in Table 5-2.

REL

is

button

in

Figure

and dB buttons simultaneously until the

now in the calibration mode. The calibration

(REL

annunciator is on).

2

through 4 for the remaining DC voltage

NOTE

5-3.

HI

and

LO

and press

MODEL

197

Figure 5-3. DC Voltage Calibration Configuration

Table

Range

200mV

2v

v

20

200

v

1000

v

197

as shown in Figure

in the exact sequence listed.

1.

Select the AC voltage function and the 200mV range.

2. Set the calibrator to output 190.OOOmV at 500Hz.

3.

Adjust the display using the STO/CLR and RCL buttons to

read 190.OOOmV AC.

4.

Press the dB button and verify that the dB annunciator is

displayed.

5.

Set the calibrator to output 19.OOOmV at

6.

Adjust the displayed reading for 19.000mV.

7. Press the off.

8.

Repeat steps 2 and 3 for the remaining ranges using Table 5-3 as a guide.

9.

Store

the

p'lragraph

5-2.

DC

Voltage Calibration

Calibrator

Voltage

+

190.000mV

+1.90000

-1.90000 +19.0000 +190.000

+1000.00

REL

button and verify that the dB annunciator is

lit317

call

5.h.S.

v

v v v

v

5-4.

Steps

constmts

Model

190.000mV

1.90000

-1.90000

19.0000

190.000

1000.00

1-6

hofon~

197

Reading

v

v v v

must be performed

500Hz.

pi-occLdins.

See

5.6.6 Frequency Compensation

..~

'9

5.6.5 AC Voltage Calibration

With the Model 197 still in the calibration mode ("C" annunciator on), connect the AC voltage calibrator to the Model

The following section is to be used to determine compensation should be performed on the Model 197, and to perform frequency compensation requires the Model 197 to be warmed up for at least one hour. Note that this section is not to be used to verify that the

if

necessary. This procedure

if

frequency

5-5

'

Model 197 desired refer to Section 3 Performance Verification.

1.

Select the 750VAC range and set the calibrator to output

500.00V at 500Hz. Press the turns on).

2. Set the calibrator to output 500.00V at 2OkHz. Verify that the reading on the Model 197 is

REL (REL

3. Set the calibrator to output 1OO.OOV at 500Hz and select the 200VAC range. Press the REL button turns on).

4.

Set the calibrator to output 1OO.OOOV at 20kHz. Verify that the reading on the Model 197 is 000.OOOV f200 counts. Press

5. Set the calibrator to output 1O.OOOOV at 500Hz and select the 20VAC range. Press REL

6.

Set the calibrator to output 1O.OOOOV at 20kHz. Verify that the reading on the Model 197 Press

AC

Voltage function is within specifications.

WARN I NG

Steps voltage. Take care not to come into contact with live circuits that could cause personal

injury or death.

1

through 4 require the use

annunciator turns off).

REL

(REL

annunciator turns off).

REL

(REL

annunciator turns off).

REL

button

000.00

(REL

k

150 counts. Press

(REL

annunciator turns on).

is

00.0000

of

high

annunciator

f200 counts.

2. Set the calibrator to output 500.00V at 20kHz. Adiuz

If

C103 for annunciator turns

3.

Set the calibrator to output 1OO.OOV at 500Hz and select the 200VAC range. Press REL

4.

Set the calibrator to output 1OO.OOV at 20kHz. Adjust c105 for a reading on the Model 197 counts. Press REL (REL annunciator turns

5. Set the calibrator to output 1O.OOOOV the 20VAC range. Press

6.

Set the calibrator to output C107 for a reading on the Model 197 counts.

7. Reinstall the top cover.

a

0

reading of

off.

\

INPUT

000.00

REL

-t50

counts. Press

(REL

annunciator turns on).

of

000.OOOV off).

at

500Hz and select

(REL

annunciator turns on).

1O.OOOOV

at 20kHz. Adjust of

00.0000V +50

HI

OUTPUT

LO OUTPUT

REL

(REL

+50

If any of the above verifications are not met by the Model 197, the top cover must be removed and three trimmer

capacitors adjusted. The adjustments must be performed

10

within circuit components will be close to normal operating temperature. The three trimmer capacitors (C103, C105 and C107) are accessible through the shield. The shield and PC board must be secured to the bottom cover in order to prevent movement. This asssembly can be secured with two screws and nuts (not supplied). Route the screws through the bottom cover through the two brown spacers to the shield. Secure the screws with the nuts. Also, use a flat blade, insulated calibration tool for all the adjustments. Perform the following steps in the exact sequence listed.

1.

Select the 750VAC range and set the calibrator to output

500.00V at 500Hz. Press the REL button turns on).

minutes after the top cover is removed

WARNING Steps voltage. Take care not to come into contact with live circuits that could cause personal

injury or detah.

1

through 4 require the use

of

(REL

so

that the

high

annunciator

Figure

Range

200mV 200rnV"

2

20

200

MODEL

5-4.

Table

v v

v

197

5200A

AC

Voltage Calibration Configuration

5-3.

AC Voltage Calibration

Calibrator Calibrator Model

Voltage Frequency

190.000rnV

19.000niV

1.90000

19.0000

190.000

v

MODEL

500Hz 500Hz 500Hz 500Hz 500Hz

5215

Reading

190.000rnV

19.000rnV

1.90000 V

19.0000 V

190.000 V

197

5-6

5.6.7

Resistance Calibration

With the Model

197

in the calibration mode

("C"

ciator on), select the ohms function and connect the calibrator to the Model

197

as shown in Figure 5-5. Four wire resistance measurements need only be done when not using the REL feature. Use the following procedure and refer to Table 5-4 to calibrate the ohms function.

1.

Select the

2OOQ

range and set the resistance calibrator

output zero ohms (short).

2.

Press the

REL

button on the Model 197. The

REL

ciator appears on the display and the display reads zero

(test lead compensation).

3.

Set the calibrator to output 190Q. Adjust the display using the STO/CLR and RCL buttons Press

REL

(REL

annunciator turns

4.

Select the 2kQ range and set the resistance calibrator to output zero ohms (short). Press REL

turns on).

-

5.

Set the calibrator to output 1.9kQ. Adjust the display reading

6.

Press the turns

7.

Select the 20kQ range and set the resistance calibrator out-

of

REL

off.

1.90000kn. button and note that the

put zero ohms (short). Press

for

a reading

off).

REL

(REL annunciator turns

(REL

REL

of

annunciator

190.000Q.

on).

8.

Set the calibrator reading

of

to

output 19kQ. Adjust the display

19.0000kQ. Press REL (REL annunciator turns

off).

9.

Repeat steps 7 and 8 for the

200k, 2M

and

20M

using Table 5-4 as a guide. For these ranges use the configuration shown in Figure 5-6.

annun-

to

annun-

for

a

for

a

ranges

NOTE

Four terminal resistance measurements need only be done when not using the

5.6.8

Calibration

MODEL

197

Storage

REL

feature.

MODEL 5450A

RSENSE

Figure

f

197

MODEL

5-5.

200, 2k

Calibration

INPUT

and

INPUT

HI

MODEL 5450A

INPUT

LO

SENSE

LO

20k

Four Wire Resistance

Figure

5-6,

200k, 2M

Cali brat ion

Table

Range

200

2

kQ

20

kfl

200

kQ

2MQ

20MQ

5-4.

n

and

20M

Resistance

Calibration

Resistance

190

Q

1.9

kQ

19

kQ

190

kfl

1.9 MQ 19

M

Two

Wire Resistance

Calibration

Model

190.000

1.90000

19.0000

190.000

1.90000

19.0000MQ

197

Reading

Q

kR

kQ

5-7

Equipment

Five function DMM with 0.1 basic DCV accuracy, 10M input impedance.

%

Use

Power supply and DC voltage checks;

analog signal tracing continuity, logic

levels.

Dual-trace, triggered sweep oscilloscope, DC

Digital Frequency Counter

to

50MHz.

5.7 TROUBLESHOOTING

The troubleshooting instructions contained in this section are

intended for use by qualified personnel having a basic understanding of analog and digital circuitry. The individual should also be experienced at using electronic test equipment as well as standard troubleshooting procedures. The information presented here has been written to assist in isolating a defective circuit or circuit section; isolation of the specific

component is left to the technician.

The success or failure in troubleshooting an instrument such

of

as the Model 197 depends not only the skill but also relies on accurate, reliable test equipment. Table lists the required test equipment and specifications recommended for troubleshooting the Model 197. Other equipment such as logic analyzers, capacitance meters (etc) could also be helpful in difficult situations.

the technician,

5-5

5.7.1 Power Up Sequence

Digital and analog waveform checks.

Checking clock frequencies.

4.

If

no problem is found by the RAM and NVRAM checks,

the Model 197 goes into the measurement mode.

If the RAM check reveals a problem, check U121. NVRAM check reveals a problem, check

5.7.2 (NVRAM test).

U113

and refer to

5.7.2 Self Diagnostic Program

The self diagnostic program is designed to aid the technician

in troubleshooting the Model 197. There are several tests that may be performed using the self diagnostic program. These tests (display, software revision level and sequential display test) are run automatically. After this sequence the Model 197 goes into the troubleshooting mode.

To use the self diagnostic program, press and hold in the dB button while turning on the Model 197. The following sequence occurs:

If

the

The software revision level of the Model 197 may be displayed upon power-up by running the diagnostic program. The diagnostic program is explained in paragraph 5.7.2.

a

When the Model 197 is turned on it goes through

sequence that is outlined as follows:

Reset-All zeroes are briefly displayed before going into

the measurement mode. During this display the Model 197 goes through a check of the RAM circuitry, and a check of

NVRAM

the

If

the

RAM

up with all zeroes. Refer to Table 2-1.

If

the

displayed:

circuitry.

circuitry has a problem, the Model 197 locks

NVRAM

test fails, the following message is

cErr

power up

1.

All LCD

2. The software revision level is then displayed (e.g.

3.

The sequential display test runs.

4.

The Model 197 goes into the troubleshooting mode.

If

the dB button is released, the instrument flags either RAM

or NVRAM self test failures, should they occur.

RAM

troubleshooting test mode.

RAM

with all zeroes displayed. Replacing U112 may correct the problem.

Non-Volatile RAM Test-If the NVRAM test fails, the following message is displayed:

digits and annunciators turn on.

Al).

If

neither

nor NVRAM fails, the instrument defaults to the

Test-If the RAM test fails, the Model 197 locks up

cErr

"This is a message indicating that the instrument is not

calibrated properly, since calibration constants are stored in NVRAM. The Model 197 remains at this point but operation may be restored ing either the "C" annunciator indicates that the unit failed the NVRAM

test.

At this point try calibrating the instrument with the constants already entered by simultaneously pressing

the CAL message is displayed. Then release the buttons. Simultaneously press the until the STOR message is displayed.

indicating that the NVRAM is probably good, a full calibra-

tion is required.

chip,

recalibrated after the problem is corrected.

Sequential Display Test-Segments and annunciators are sequentially displayed in eight steps. Use Figure ment identification. The steps are

1.

The "a" segments of the digits, the dB and V annunciators are displayed.

2. The "b" segments

3.

The "c" segments of the digits are displayed.

4.

The "d" segments

(mA)

5. The "e" segments of the digits are displayed. Also, the minus sign,

6.

The AUTO, BAT, m(mV) and c annunciators are displayed.

7.

The

and k annunciators are displayed.

8.

The decimal points, most significant digit and the STO,

and A annunciators are displayed.

REL,

dB

or

If

the error persists try replacing the NVRAM

U113.

Again the Model 197 must be completely

of

the digits are displayed.

of

RCL

and

RMT

REL,

M and Q annunciators are displayed.

"f"

segments of the digits are displayed. Also, the

"g"

segments of the digits are displayed. Also, the AC

for

troubleshooting by press-

DATA Logger buttons. The flashing

REL

and dB buttons again

If

as

the digits are displayed. Also, the m

annunciators are displayed.

if

the test fails,

REL

and dB until

REL

and dB

the error is corrected,

5-7

for

seg-

follows:

Troubleshooting Test Modes-The troubleshooting mode designed to switch on various switching relays and logic levels to allow signal tracing through the instrument. The first displayed mode reflects the selected function and range. For example; assume that

In this case,

0 is the test number.

u

corresponds to the volts function.

1

corresponds to the 200mV range.

The test number can be changed by pressing in the dB button. Table

5-6

lists test modes for all functions and ranges.

Troubleshooting consists and using the data found in Table cuit.

NOTES:

1.

When a different function ton must be pressed and held in to update the display with the corresponding test mode.

2. Do not use AUTO when in AC

3.

Use AUTO when checking circuitry on the 20M and 200MQ range

5.7.3

Power Supply and Battery Pack (Model

1978)

Table 5-7 shows the various checks that can be made to the power supplies

p

normal voltage checks, it is a good idea to check the various supplies with an oscilloscope for signs of noise

(006,

Checks

of

the Model 197 and 1978. In addition

of

selecting the desired test mode

5-6

or

range is selected, the dB but-

or

106,

206,

306

FETs,

transistors,

"Oul"

is displayed.

to signal trace the cir-

DC volts.

and

406).

or

oscillations.

to

is'

the

Figure

a

fl-I

9

C

el

5-7.

Segment Identification

I

d

5.7.4

A/D Converter and Display

Make sure the A/D converter and display are operating perly BEFORE attempting to troubleshoot the signal condi-

tioning circuits. Check these circuits using the information Table 5-8 and 5-9.

5.7.5

Signal Conditioning

These circuits can be checked by using the diagnostic pro-

gram (troubleshooting modes). See paragraph 5.7.2.

refer to Table 5-6.

pro-

in

Also,

5-9

Table

5-6.

Model

197

Troubleshooting Mode

Function

and

Range

200rnVDC

Test

Mode

ou

lul 2u 1 3u

2VDC ou2

1 u2 2u2 3u2

20VDC Ou3

1

u3 2u3 3u3

200VDC

Ou4

1 u4 2u4 3u4

1 kVDC

Ou5

1

u5 2u5 3u5

200rnVAC ou 1

lul

2u

3u 1

2VAC ou2

1 u2 2u2 3u3

20VAC Ou3

1 u3 2u3

3u3

200VAC Ou4

1

u4 2u4 3u4

750VAC Ou5

1 u5

2u5

3u5

DCA

All

Ranges

OA 1 -0A6

1 A1 -1 A6 2A 1 -2A6 3A1-3A6

200Q

00

101 20 1 30

1

DC

Gain

u102

XI0 XI0

XI0

Amp

XI XI

x1

XI XI

XI

XI XI

XI XI XI XI

XI0

XI XI

XI0

XI XI

AC

Amp

Gain

U104

x5 x5 x5 x5

XI XI XI XI

XI XI XI

XI XI

XI XI XI

XI

Multiple8

On

FET

0111 01 12 01 13

0112 0111

01 12

0113

0112 0111

01

10

01 13

01 12 0111

0110

0113 0112

0111 01 10 01 13 0112

0111 01 12 01 13 01 12

0111 01 12 01 13 0112

0111 0112 0113 01 12

0111 0112 01 13

01

12

0111

01

12 0113 01 12

0111 0112 01 13 01 12

0113 0112 0111 0110

Range

Transistor On

0104, 0105 0104, 0105 0104, 0105

0104. 0105

0104, 0105, 0106, 0107 0104, 0105, 0106, 0107 0104, 0105, 0106, 0107 0104, 0105, 0106. 0107

0104, 0105, 0109, 0108 0104, 0105, 0109, 0108 0104, 0105, 0109, 0108 0104, 0105, 0109, 0108

0104-0107, 0118

0104-0107, 0118 0104-0107, 0118

0104-0107, 0118 0104-0107, 0118 0104-0107. 0118

0104, 0105, 0106, 0107 0104, 0105, 0106, 0107 0104, 0105, 0106, 0107 0104, 0105, 0106, 0107

0104, 0105, 0108, 0109 0104, 0105, 0108, 0109 0104, 0105, 0108, 0109

0104. 0105. 0108, 0109 0104, 0105

0104, 0105 0104, 0105

0104. 0105

0104, 0105 0104, 0105 0104, 0105

0104. 0105

Range Control

:

3

Levels

PA0

0

1

0

~

0 0 0

0

-

0

0 0

__

0 0

0

0 0

0

~

0

___

0

0 0 0

1

0

1

0

0 0

1

0

~

1

0

~

On

U

0

1

I0

010

Ojl

010

10

00

01

00

10

00

01

0

~

1

0

1

0 0

0

~

1

0 0

0

1

0

~

0

1

0

~

1

0

1

0 0

0

~

0

1

0

1

0

~

0

1

0

~

1

0

1

0

~

0

1

0

1

0

~

5-10

Table

5-6.

Model

197

Troubleshooting Mode (Cont.)

Function

and

Range

2kQ

20kQ

200kQ

2MQ

20M

Et

200M

(Auto)

ACA

All

Ranges

Test

Mode

002

102 202 302

003

103 203 303

004

104 204 304

005

105 205 305

006

106 206 306

OA 1 -0A6

1

A1

-1

A6

2A

1

-2A6

3A

1

-3A6

DC Amp

Gain

u102

XI XI XI XI

AC

AmD

Gain U104

x5 x5 x5 x5

M

ul

ti

plexer Range

FET On Transistor On

Q104, Q105 0104, 0105 Q104, 0105

Q110 0104, Q105

01

13

0104, 0105,

Q108,

Q112 Q111 Q110

Q113 Q112 Q111

0104, 0105, Q104, 0105, 0104, 0105,

0108,

Q108,

Q110

01

13

Q112

0111

Q110

Q104, Q105 Q104, 0105 Q104, Q105

0104. 0105

Q113

01 12

Qlll

Q113

Q111

Q112

Q113 Q112

Q109

Q109 Q109 Q109

Range Control

~

0

00

00 00

10

01

00

10

00

01 00

10

00 0

'1

I

0

01

1

01

0

01

5.8

SPECIAL HANDLING

OF

STATIC-

SENSITIVE DEVICES

CMOS

pedance levels for low power consumption. As a result, any normal static charge that builds up on your person clothing may be sufficient to destroy these devices if they are not handled properly. Table 5-10 lists all the static sensitive devices in the Model 197. When handling these devices, use the following precautions to avoid damaging them.

1.

devices are designed to operate at very high im-

or

The devices listed in Table 5-10 should be transported and

handled only in containers specially designed to prevent static build up. Typically, these devices will be received in

static-protected containers. The parts should remain there until ready for installation.

2.

Remove the devices from their protective containers only at a properly grounded work station. Always ground yourself with a suitable wriststrap.

3.

Handle the devices only by the body. pins.

4.

Any printed circuit board into which the device is to be inserted must also be grounded to the bench or work station.

5.

Use only grounded type solder suckers.

6.

Use only a grounded type soldering iron.

7. Once the device is installed on the adequately protected and normal handling may resume.

Do

not touch the

PC

board, the device is

5-1

1

Table

itep

Item/ComDonent

~

1

5102 F102 Line Fuse

2

Line Cord

3

4

Power ON/OFF switch pin 6

5

U109 pin 2 U109 pin 3

6

0126 collector or U116 pin 7

7

Power ON/OFF switch pin 12

8

U107 pin 2

9

10

U107 pin 3

11

Q128 Emmitter

12

U116 pin 3 U116 pin 2

13

Q126 Emitter

14

0123 Emitter or J1009 pin 7

5"

*

16*

Q101 Base

17"

UlOl pin 8

U102 pin 7

18"

*Battery option (1978) checks.

""If Q123 is replaced, be sure that the device is properly seated on the mother board

IEEE

board (if installed).

5-7.

Power Supply and Battery Pack (Model

Reauired Condition

Set to 115V or 230V as required. Continuity Plugged into proper line recep-

tacle; power

+

13V to + 16.5V +6.4 +6.4 +5%

+1

ov

-15V *lo%

-6.4V *lo%

-6.4V +lo%

-9.ov, +5% +5v &5% +5v *5% +5.0V +5.0V f 10%

0.6V while charging. Power

switch

>

10.8V Line cord disconnected,

battery pack charged and power

on

+

5V with batteries charged.

f5%

f1

0%

f5%

off.

on.

1978)

Remarks

S102 is externally accessible from rear panel.

+

V power for regulator circuitry.

Virtual Reference.

Reference Zener.

+

1ov Supply

-V power for regulator circuitry. Inverting input for U107. Low noise negative supply reference.

-9v Supply

+

5V supply reference.

Inverting input for U116.

+

5V analog supply.

+

5V digital supply.

Current Sink Voltage Inverter

Voltage Comparator

Checks

so

that

it

will not touch the

Step Item/Component Required Condition

12 P1006, pin 5 3 P1006, pin 6 4 P1006, pin 7 +5v +5%

5 P1006, pin 2 81.92kH.z

6 P1006, pin 1

7 P1006, pin 12

8 P1006, pin 13 OV to +5V Pulses

9 P1006, pin 14

10 LCD Verify that thet LCD is properly posi-

11 Connector (P1006) Check that connector is not reversed. 12 Strip Connector Verify that they are positioned properly.

5-12

Turn on power; select the 2V range.

+

3.3v

+

1.66V

OV to +5V Pulses OV to +5V Pulses

+5V to OV Pulses

tioned.

Remarks

Vlcd 1 Vlcd2

Power to Display Clock Data From pp. Data From pp. Data From yp. Data From pp.

Table 5-9. A/D

-

Step

ltem/ComDonent I Reauired Condition

___

1

2

U124 pin 38 U119 pin 10

3

U119 pin 6

4

U119 pin 5

5

U119 pin 7

6

7

U119 pin 12

U118 pin 6

8

UllO pin 6

9

U108B pin 7

10

U117 pin 6

11

U105A pin 15

12

U105A pin 10

13

U117B pin 9

14

~

Turn on power; select 2VDC range.

Short the input.

3.276800MHz Clock

655.36kHz Clock

81.92kHz Clock

40.96kHz Clock

163.84.kHz Clock

1.28kHz Clock

+

5V to = OV pulse train, 3psec in duration every 22psec. (Set signal to end charge balance pulse.)

Integrator Waveform.

Variable waveform OV to

1

Variable pulse train, OV to + 5V

Variable pulse train, OV to +5V.

4msec pulses approximately every

150msec. OV to +5V.

50msec and 100msec pulses

Converter/Microcornputer

Crystal Frequency (Y101) AID tirnebase and

address strobe. Clocks for U117A.

generator signal.

Q4

Timebase for real time

pP

S1 input

+

5V.

Comparator Output

Charge Balance Current

Checks

Remarks

pP

Minimum pulse

Generates set for U117A. (proper phase

and Q3 required).

interrupt.

of

U118B.

(Charge Balance)

Control. U124 Timer Input Single Slope Control

Line Integrator charge

Balance Control

of

Table 5-10. Model 197 Static Sensitive Devices

Circuit Designation

0104, Q107

(2108, QllO Q111, (3112

Q113

u101

U105

U107 U113 U114 U115 U117 U118 u119 u120 u121 u122 U123 U124

Keithley Part

TG-139

TG-I39 TG-139 TG-I39

IC-415 IC-283 IC-347 IC-353

LSI-61 IC-143 IC-337

IC-341

IC-348

IC-351

LSI-62

197-800-**

IC-338

LSI-60

No.

5-13/5-14

SECTION

REPLACEABLE PARTS

6.1

INTRODUCTION

This section contains replacement parts information, component location drawings and schematic diagrams for the Model 197 and Model 1978.

6.2

REPLACEABLE PARTS

Parts are listed alpha-numerically in order of the schematic designation. Table 6-1 contains parts list information for the mother board. Table 6-2 contains parts list information for

the display board. Parts list information for the Model 1978 Battery Pack is contained in Table 6-3.

6.3

ORDERING INFORMATION

To

place an order, or to obtain information concerning replacement parts, contact your Keithley representative the factory. See the inside front cover for addresses. When ordering include the following information:

1.

Instrument Model Number

2. Instrument Serial Number

3.

Part Description

4.

Circuit Designation

5.

Keithley Part Number

(if

applicable)

or

6

6.4

FACTORY SERVICE

If

the instrument is to be returned to the factory for service, photo copy and complete the service form which follows this section and return

6.5

SCHEMATIC DIAGRAMS AND

COMPONENT LOCATION DRAWINGS

The component location drawings and schematic diagrams, are presented as follows:

Figure 6-2. Model 1978 Battery Pack, Component Location

Drawing, Dwg. No. 1978-100.

Figure 6-3. Mother Board, Component Location Drawing, Dwg.

NO.

197-100.

Figure 6-4. Display Board, Component Location Drawing, Dwg.

NO.

197-110.

Figure 6-5. Mother Board, Schematic Diagram, Dwg. 197-106.

Figure 6-6. Display Board, Schematic Diagrm, Dwg. 197-116.

Figure 6-7. Model 1978 Battery Pack, Schematic Diagram, Dwg. NO. 1978-106.

it

with the instrument.

No.

If

an additional instruction manual is required, order the manual package (Keithley Part Number 197-901-00). The manual package includes an instruction manual and all pertinent addenda.

6-1

-

/’.

11

.

-

I

WINDOW BEZEL

J

,RETAINER

175-305

MASK

175 306

__

LCD

DD-36

175-307

6-2

Figure

6-1.

Display

Assembly

Exploded

View

Table

6-2.

Display Board, Parts

List

Schematic

Desig. DS-201

PI006 u201

Schematic

Desig. BTlOl

ClOl

c102 CR101 PI009 R101

R102 R103 R104 R105

0101

U101" u102

*Static Sensitive Device

Description

5 1/2 Digit Liquid Crystal Display (LCD)

Cable Assembly (14 Conductor) LCD Controller/ Driver Retainer, Strip Connector

Strip Connector (2 required) LCD Mask

Window Bezel

Switch Pad, Conductive Touch

DescriDtion Battery Assembly, 12.0V Sealed Rechargeable NiCad

Capacitor, 250pF, 25V, Aluminum Electrolytic Capacitor, IOpF, 25V, Aluminum Electrolytic

Rectifier, Schottky Barrier, 1 N5820

Cable Assembly, 10 Conductor

Resistor, 4.7f2, lo%, Resistor, 4.7Q2, Resistor, 44.2k, 1 Resistor, 37.4k, 1 Resistor, 1.2M, 5%, 1 /4W, Composition

Transistor, NPN, High Voltage (TIP-49) Voltage Converter, S17661 CJ

Voltage Comparator, LM393 Heat Sink used on UlOl

Standoff (Battery Board to Shield)

Table

6-3.

IW,

YO,

1 /4W, Composition

%,

1 /8W, Metal Film

YO,

1 /8W, Metal Film

Model

Fixed, Fusible, Wound

1978

Battery Pack, Parts List

Location

Sch Pcb

D2 D3 B4 C4 D3 C4

Location ;ch Pcb

-

B3

D2 E4 D3 C4

D2 D4 D2 B1

E2 C3 El

C2 E3 E3 E3 E4

D3 E3 D3 C2 D3 04

D3 E3

D3

-

D3

-

Keithley Part

No.

DD-36 CA-30-2 LSI-59 175-307

CS-460-2 175-306

175-305

175-308

Keithley Part

No.

BA-40

C-314-220

C-314-10

R

F-53

CA-27-1

R

-334-4.7 R-76-4.7 R

-88-44.2k R

-88-37.4k

R-76-1.2M

TG-I37

IC-340 1C-343

H

5-28

6-6

Figure

6-2.

Model

Drawing, Dwg.

1978 Battery Pack, Component Location

No.

1978-100

6-7/64

Figure

6-3.

Mother Board, Component Location Drawing,

Dwg.

No.

197-100

(sheet

1 of

2)

6-916-10

Figure

6-3.

Mother Board, Component Location Drawing,

Dwg.

No.

197-100

(sheet 2 of

2)

6-11 /6-12

Figure

6-4,

Display Board, Component Location Drawing,

Dwg.

NO.

197-110

6-1316-14

Figure 6-5. Mother Board, Schematic Diagram, Dwg.

197-106 (sheet 1

of

21

6-1516-16

No.

Figure

6-5.

Mother Board, Schematic Diagram, Dwg.

197-106

(sheet

2

of

2)

No.

6-17/6-18

Figure

6-6.

Display Board, Schematic Diagram, Dwg.

197-116

6-19/

No.

6-20

Figure 6-7. Model 1978 Battery Pack, Schematic Diagram,

Dwg.

NO.

1978-106

6-21

16-22

+

Instruments Division, Keithley Instruments, Inc.

WEST GERMANY: GREAT BRITAIN:

FRANCE NETHERLANDS SWITZERLAND. AUSTRIA ITALY:

Keithley Instruments GmbH Keithley Instruments, Ltd. The Minster Keithley Instruments SARL 3 Allee Keithley Instruments BV Keithley Instruments SA Kriesbachskr. 4 8600 Dubendorf Keithley Instruments GesmbH Rosenhugelstrasse Keithley Instruments SRL Viale

.

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des Garays B.P.

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28775 Aurora

5

-

Munchen

58,

Porhnan Road Reading, Berkshire

49 4202

4/A 20146

Road Cleveland,

70 089-71002-0

60 91124

MS Gorinchem

01-821-9444

12

A-1120

Milano

Palaiseau/Z.I.

P.O.

Vienna

02-4120360

+

Telex:

52-12160

KG

1-6-0115 155

Box

559 4200

Telex:

(0222) 84 65

or

Ohio

3

IEA

828 472

48

02-4156540

Fax:

AN

Gorinchem

Fax:

Telex:

44139

089-7100259

011 44

731

Telex:

0222-315366

131677.

Fax:

(216)

575

6h6

600 933

01830-35333

Fax:

024121249

248-0400

Fa\.

fkx

(0222)

tLz035')7

Fax:

Oil

4%

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l-h-~lll772h

T&\.

21

2-16-6168

5%

4hY

h8-I.

FJ\

lilS3O-.~OX?I

Keithley 197 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual