Tektronix 5900 Instruction Manual

INSTRUCTION MANUAL

Digital Multimeter

Model 5900

WARRANTY

We warrant each of our products to be free from defects in material
and workmanship. Our obligation under this warranty is to repair
or replace any instrument or part thereof which, within a year after
shipment, proves defective upon examination. We will pay local

domestic surface freight costs.
To exercise this warranty, write or call your local Keithley repre-

sentative, or contact Keithley headquarters in Cleveland, Ohio.
You will be given prompt assistance and shipping instructions,

REPAIRS AND
CALIBRATION

Keithley Instruments maintains a complete repair and calibration
service as well as a standards laboratory in Cleveland, Ohio. A
service facility is also located in Los Angeles for our west coast
customers.

A Keithley service facility at our Munich, Germany office is
available for our customers throughout Europe. Service in the

United Kingdom’can be handled at our office in Reading. Addition-

ally, Keithley representatives in most countries maintain service

and calibration facilities.
To insure prompt repair or recalibration service, please contact

your local field representative or Keithley headquarters directly
before returning the instrument. Estimates for repairs, normal
recalibrations and calibrations traceable to the National Bureau of
Standards are available upon request.

KEITHLEY

The measurement engineers.

Keithley Instruments, inc., 28775 Aurora Road, Cleveland, Ohio 44139. [phone]

European Headquarters: Heiglhofstrasse 5, D-8000 Munchen 70 West Germany, [phone]

Unlted Kingdom: 1 Boulton Road, Reading, Berkshire, [phone]

France: 44 Rue Anatole France. F-91121 Palaiseau (01) 928-00-48

FOR YOUR SAFETY

Before undertaking any maintenance procedure, whether it
be a specific troubleshooting or maintenance procedure
described herein or an exploratory procedure aimed at
determining whether there has been a malfunction, read the
applicable section of this manual and note carefully the
WARNING and CADTlON notices contained therein.

The equipment described in this manual contains voltages
hazardous to human life and safety and which is capable of
inflicting personal injury. The cautionary and warning
notes arc included in this manual to alert operator and
maintenance personnel to the electrical hazards and thus
prevent personal injury and damage to equipment.

If this instrument is to be powered from the AC Mains
through an autotransformer (such as a Vartac or equivalent)
ensure that the instrument common connector is con­nected to the ground (earth) connection of the power
mains.

Before operating the unit ensure that the protective con­ductor (green wire) is connected to the ground (earth)
protective conductor of the power outlet. Do not defeat

the protective feature of the third protective conductor in

the power cord by using a two conductor extension cord or
a three-prong/two-prong adapter.

Maintenance and calibration procedures contained in this
manual sometimes call for operation of the unit with power
appliedandprotective covers removed. Read the procedures
carefully and heed Warnings to avoid “live” circuit points
to ensure your personal safety.

Before operating this instrument,

1. Ensure that the instrument is configured to
operate on the voltage available at the power
source See Installation section.

Ensure that the proper fuse is in place in the

2.
instrument for the power source on which the
instrument is to be operated.

3. Ensure that all other devices connected to or in
proximity to this instrument are properly grounded
or connected to the protective third-wire earth

ground.

COPYRIGHT

0

Copyright
States of America.
not be reproduced in any form without written permission of the
publishers.

1976 by Keithley Instruments, Inc. Printed in the United

All rights reserved. This book or parts thereof may

PROPRIETARY NOTICE

This document and the technical data herein disclosed, are proprietary

to Keithley Instruments, Inc., and shall not, without express written
permission of Keithley Instruments, Inc., be used, in whole or in part
to solicit quotations from a competitive source or used for manufacture
by anyone other than Keithley Instruments, Inc. The information
herein has been developed at private expense, and may only be used for
operation and maintenance reference purposes or for purposes of
engineering evaluation and incorporation into technical specifications
and other documents which specify procurement of products from

Keithley Instruments, Inc.

TABLE OF CONTENTS

Section

1

1.1

1.7

1.9

1.11

1.13

1.15

1.17

1.19
I .26
I .32

2

2.1

2.4

2.6

2.8

2.12

2.13

2.16

2.18

2.19

2.21

2.23

2.24

2.28

2.42

2.44

2.46

2.48

2.50

2.54

2.56

2.59

2.60

2.62

2.64

2.66

2.68

2.70

2.72

2.75

2.77

GENERALDESCRIPTION

Introduction

Options .’

Model 42 Remote Programming

Rear Input Options(-I, -1s)

Rack-Mounting Flanges (403402)
High-Voltage Probe
Current Shunt Set (651)

Electrical Description
MechonicalDescription
Specifications

mSTALLATION& OPERATION
Unpacking and Inspection
Bench Operation
Rack Mounting
Power Connections
Input/Output Cabling

Binding Posts
Rear Input Connector

Manual Operation

Controls

Display ...............

Measurement Connections.

Basic Voltage Measurement

Ohms Measurement

Ratio Measurements
System Capabilities

Printer Output
Program Input.

Logic Levelsand Electronic Interface

Driving the Inputs
TTL Loading Conditions

Exceptions to Input Loading Conditions

‘ITL Output Capabilities
Thning Sequence
Other Read CommandOptions
Reading Rates.

Superfast

Printer Output

Numerical Data

Function Data.

Range Data.

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

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

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

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

. JZOI .........

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

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

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

.........

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

..........

.........

...........

........

.......

..........

..........

...........

...........

..........

........

........

...........

......

...........

...........

...........

Title Page

. .

.....

...

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

1.2
1-2
l-2
1-2
I.3
l-3

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

2.4
24
24
2-7
2-7
2-8
2-8
2-8
2-B
2-8

2.10
2-10

2.10

2.11
2-12

2.12
2-13
2-13

‘2.14

2.14

111

980453

Section

TABLE OF CONTENTS (continued)

2.79

2.81

2.83

2.84

2.86

2.88

2.90

2.93

2.95

2.97

“NO” Indication
Status Output Lines

Input Control Lines
System Direct Command
Remote Programming
SystemControl

Function Programming

Range Programming

+ Five Volts

Hold

2.99 Read Commands

2.101

2.103

2.105

2.107

2.109

Timeouts

Data Inhibit
Program Storage

Superfast

Adding/Removing Accessories

3 SPECIFICATIONTESTS .....

3.1

3.4

3.6

4

4.1

4.3

4.5

4.7

General ...........

Required Equipment ......

Procedure ..........

THEORY OF OPERATION
General

Mechanical Description
Electrical Description
Signal Conditioning Section

4.10 Switching Board

4.14

4.18

4.2 1

4.24

4.28

4.30

4.33

4.35

4.37

4.52

4.54

4.56

4.70

4.12

4.74

OhmsConverter
Scaling Atnplifier
Averaging AC Converter

RMSACConverter
Attenuator
Isolator
Switching Bypass.

Integration

Digitizer,

Ratio, Standard
Ratio,Option
Display Board

Main Logic and Control Circuitry

Control Logic
Program Cycle

. .

2.14

2.15
2-15

2.16

2.16

2.16

2.16

2.17

2.17
2-17

2.17

2.17
2-17

2-17

2.18

2.18

3.1
3-l
3-l
3-1

4.1
4-l

4-l
4-l
4-1
4-l
4-1

4.3

4.9
4-9

4.9

4.9
4-9
4-9

4.12
4-14

4.15

4.15

4.17
4-17

4.19

iv

TABLE OF CONTENTS (continued)

980453

Section

4.76 Display Logic

4.78 Superfast

4.80

4.82
5

5.1

5.3

Power Supplies
Program.

CALIBRATION
scope

General

5.5

5.7

5.10

5.19

5.23

Preliminary Procedure

5.24

5.26

5.28

5.30

5.32

Recalibration Procedure .

5.34

5.35

5.36

5.38

DC Range Calibration
Ohms Calibration.

5.39

5.40

5.41

Ohms Range
AC Calibration (Model 33).

5.42

5.43

5.44

5.45

5.46

RMS AC Calibration (Model 32)
4-Wire Ratio Calibration
Troubleshooting

5.48

5.50

5.52

5.54

5.55

5.86

Board Revision

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

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

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

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

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

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

Required Equipment

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

Fabricated Calibration Equipment

DC Voltage Sources

AC Voltage Sources

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

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

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

Warmup.

Familiarization
Calibration Points
Environmental Considerations

Isolator Zero

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

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

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

...........

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

DC Voltage Zero and Gain.

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

ohms Zero

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

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

AC Converter Zero

Frequency Response

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

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

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

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

Troubleshooting Equipment

Power Supply Check

Operational Check

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

Preliminary Instrument Setup
Circuit Descriptions

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

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

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

...........

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

Title

..........

4-19

4.19

4.19

4.20
5-1

5-l

5-l

5-l
5-l
5-l

5-4

5-4
s-4
54
54
5-4

54

5-6
5-6
5-6
5-6

5.6
5-7

5.7

5.7
s-7
5-9

s-10

s-10
s-10
S-10
5-l 1
5-1 1

5.11
s-14

1

DRAWINGS . . . . .

PARTS LIST . . . . . . . . . . .

6-1
7-1

v/vi blank

LIST OF ILLUSTRATIONS

Figure

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

2.10

2.11

2.12

2.13

2.14

2.15

2.16

2.17

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10

4.11

4.12

4.13

4.14

4.15

4.16

4.17

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

1.1

1.2

Block Diagram -Model 5900
Dimensions,
Rack Mount Installation’
Cabling Diagram, Binding Posts
Cabling Diagram, Rear Input
Readout
Front Panel
Basic Voltage Measurement Connections
Maximum RMSlnput Voltage
Two Wire Ohms Measurements
Four Wire Ohms Measurement
Rear Panel
Measurement Sequence.
Command Timing
Minimum Read Rate vs. Input
Superfast Read Rate (Worst Case)
Pin Assignments 5201 PRINTER OUT

Pin Assignments 5202 PROGRAM INPUl
Jumper Location

Mechanical Assembly
Signal Flow, Loaded DVM.
Switching Board
Signal Flow of Switching Board

Ohms Converter

OhmsMeasurement Systems
Scaling Amplifier
Averaging AC Converter

RMS AC Converter
Attenuator/Isolator DC.
Signal Flow, Switching Bypass
Digitizer.

Integration Timing Diagram

4.Wire Ratio Option
Display Board
Main Logic&Control Block Diagram
Program Block Diagram.

10 Volt Source
Generating Accurate DC Levels
AC Source

Adjustment Locations

Ohms Input Connection

Connections for Ohms Range Adjustment

4.Wire Connections
AC Adjustment Locations

4.Wire Ratio Adjustment Locations

Title Page

l-2

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

2.4
2-4
2-s
2-6
2-8
2-9

2-11

2.12

2.13
2-14
2-16

Z-IX

4-2

4.3
4-4

4.5
4-6
4-7
4-R
4-8

4.10

4.11

4.12
4-13

4.14
4-1s

4.15
4-18

4-20

5-2
s-2
s-3
s-s
S-6

5.7
s-7
S-8

S-IO

vii

980453

LIST OF ILLUSTRATIONS (continued)

Figure

6.1

Layout, Logic and Interconnection

6.2 Layout, Readout

6.3

6.4

6.5

6.6

6.7

6.8

Schematic, Logic and Interconnection ..........

Schematic, Power Supply

Layout, Attenuator
Schematic, Attenuator
Layout, Switching
Schematic, Switching

6.9 Layout, Isolator

6.10

6.11

6.12

Schematic, Isolator

Layout, IOV Reference Amplifier
Layout, Digitizer

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

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

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

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

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

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

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

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

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

...........

...........

6.13 Schematic, Digitizer and 1OV Reference Amplifier ......

6.14

Layout, Program

6.15 Schematic, Program

6.16

layout, Display

6.17 Schematic, Display

6.18

6.19

6.20

Layout, AC Converter

Schematic, AC Converter

Layout, RMS Converter

6.21 Schematic, RMS Converter

6.22

6.23

Layout, Scaling Amplifier
Schematic, Scaling Amplifier

6.24 Layout, Ohms Converter

6.25 Schematic, Ohms Converter

6.26

Layout, 4.Wire Ratio

6.27 Schematic, 4.Wir-s Ratio

6.28 Layout,RearPanel

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

6.29 Layout, Parallel Front-Rear Input (-1) ..........

6.30 Layout, Switchable Front.Rear Input (-IS) ........

Title

Page

6-3

6.3
6-S
6-7

6.8

6.9
6-10
6-11

6.12

6-13

6.14

6.14
6-15

6.16

6.17

6.18

6.19

6.20
6-21

6.22

6.23

6.24

6.25
6-26
6-27

6.28

6.29

6.30

6.3 1
6-32

viii

LIST OF TABLES

Table

1.1

1.2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

3.10

3.11

3.12

4.1

4.2

4.3

4.4

4.5

4.6

4.7

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

5.10

7.1

7.2

Measurement Capability
Specifications
Operating Controls
Maximum Input Voltage
Positive True Logic Relationships
Range Codes(Printer Output)
Function Programming
Range Codes(Programmet)
Timeouts
Maximum Input Voltage
Required Equipment
DC Range Check(Low Ranges)
DC Range Check (High Ranges)

3.Wire Ratio Check

4.Wire Ratio Check
DC Input Resistance.
Model 33 AC Converter Range Check
Model 32 AC Converter Range Check
Ohms-Megohms Range Check.
Common Mode Rejection (In DC Volts Function)
Normal Mode Noise Rejection (In DC Volts Function)
Common Mode Rejection (In AC Volts Function)
Switching Board Range Decode
Range Switch Code
Autorange Logic
Relay Logic Coding
Annunciator Logic

“NO” Annunciator Logic
Program Logic Conversion
Required Calibration Equipment
Fixed Voltage Dividers
DC Source Accuracies
AC Source Accuracies
Power Supply Check
OperationalCheck

Trollblesllooting Guide
Troubleshooting Chart-Digitizer and 1OV Reference Amplifier
Troubleshooting Chart. Isolator and Attenuator Boards
Troubleshooting Chart

Table7.1
List of Suppliers

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

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

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

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

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

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

.............. 1 1 : : 1 1 1 1 1 1 1 1 1 :

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

............... : : : : : : : : : : : ,: : : : :

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

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

.......... : : : : : : : : : : : : : : : :

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Optional Accessories

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

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

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

: : : : : : : : : : : : : : :

............. : : :

: : : : : : : : : : : : : : :

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

: : : : : : : : :

: : : : : : : : : : : : :

: : : : : :

: : : :

: : : : : : : : :

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

Page

1-1
1-4

2.3

2.4
2-a

2.15

2.17

2.17
2-18

2.18
3-1

3.2
3-3
3-4
3-s

3.6
3-7
3-8

3-9
3-10
3-11

3.12

4-1

4.16
4-16

4.16

4.17

4.17
4-2 1

5-a
S-l
s-3
s-4

S-II
s-1 1
s-12
s-13
s-14

s-14

7-1
7-l

980453

ix

SECTION 1

GENERAL DESCRIPTION

1.1 INTRODUCTION.
The Model 5900 Digital Multimeter is a five-decade

1.2
instrument with a sixth digit providing 60% overrange. The
basic instrument is equipped for dc and dc/dc ratio meas­urements on five ranges. With the addition of the optional
AC Converter, a-c and ac/dc ratio measurements on four
ranges are available. The Ohms Converter, also optional,
adds ohms measurements on eight ranges. Complete meas­urement capability of a fully equipped instrument is tabu­lated in table 1 .l.

Table 1 .I - Measurement Capability

r

DC & Dc/Dc

RATIO

Range (Basic 5900)

.lV I x I

1vI x I

I

1ov X

FUNCTION

OhIllS

(Model 52

Ohms

Converter)

I

AC & AC/DC

RATIO

(Model 32

or 33

AC Converter)

1

IOOV I x I

ooov I x I

100.

I

.I KS2 X

I x

until a single reading is commanded by an external com­mand. The new measurement is then held until the next
external command. In Periodic mbde (RATE control CW),
measurements are made automatic+ly at the rate of approxi­mately four per second.

1.5 The basic Model 5900 includes an analog output
voltage that is proportional to the parameter being meas­ured (except ratio). The voltage, at 20 volts maximum, is
available at a rear panel connector.

Also included as standard equipment is a solid-state

1.6
isolated BCD output. TTL-compatible output levels of the
reading, function, range, etc., plus a print command are
provided. An additional line enables a new reading to be
commanded externally. An optional isolated remote pro.
gramming unit (Model 42) allows all operating commands to
be made extcmally.

1.7 OPTIONS.

1.8 All optional accessories having model numbers are
plug-in circuit boards that may be added at any time. A
calibrated accessory board can be installed without af­fecting the d-c calibration of the basic instrument. An
instrument shipped without PCB accessories will not be
equipped with a Function Switching PCB assembly. This
board must be added when accessory boards are installed.
Analog accessories are identified in table 1 .l.

1Kn

10Kn 1

100 K$-l 1

000 KS2 1

lOMa/

lOOMa 1

1.3 Range can be selected manually or automatically
(autorange).
ular measurement is selected automatically (full scale is de­fined as “100000” on any range). The instrument “up
ranges” at 16U% of full scale and “downranges” at 15% of
full scale. Polarity selection is also automatic and is dis­played on the readout.

1.4

(RATE control on EXT), a measurement is held (displayed)

In AUTO range, the proper range for a partic-

Two operating modes are provided. In Hold mode

X
I x
I x

I x
I x

I x

Model 42 Remote Programming.

1.9
The Model 42 Remote Programming accessory al-

1.10

lows the selection of function, range, filter, read command,
etc., to be made externally. Auto range selection is also
provided and appropriate timeouts are generated internally
when ranging takes place. Remote Programming “overrides”
all manual control settings to prevent erratic selections.
Complete isolation of the programming unit is achieved by
the use of photoauplers and pulse transformers.

1.11 Rear Input Options (-1, -lB, -1s. -1SB).

1.12

5900 DMM. The option designated -1 or -IB consists of
connector 5204 on the back panel with input lines +
INPUT, + CURRENT, and GUARD wired in parallel with
the front panel input terminals; the option designated -1s
or -1SB is the same as the -1 or -lB except that the front or
rear inputs are selectable by a switch on the front panel.

Two rear input options are available for the Model

b

I-I

980453

T T

1.13 Rack-Mounting Flanges (403402).

1.14 Rack.Mounting Flatages are used where 1111’ IIIS~~U-

ment is to be installed in a relay-rack or cabinet.

1.15 High-Voltage Probe (641).

1.16 The High.Voltage Probe extends the voltage range of
the instrument up to 10,000 volts (or 7SOOV rms). It is an
insulated prube containing a 1000: 1 voltage divider.

l-2

1.17 Current Shunt Set (651).
I .I8 The Current Shunt Set consists of six precision

sIllill assemblies witb values selected to produce a voltage
drop that, n~e:tsured in millivolts. Ins a numerical value
cqual to 111~ current Ilow in milliamps or micro;tmps.

1.19 ELECTRICAL DESCRIPTION.

1.70

1be Model 5900 DMM is a dual slope integration

instrument consisting of three main functional areas: signal

9804.53

conditioning, integrating, and control/display. A block dia­gram of the instrument is shown in figure I, 1.

1.21 The signal conditioning section includes the
Switching p-c board, AC Converter, Ohms Converter,
Attenuator, and Isolator. The function of these circuits is
to convert the incoming signal to 10 MC, full scale into the

integrator.

1.22 The Integrating section consists of the Integrator

amplifier, Null Detector and + reference voltages. The
function of these circuits is to convert the conditioned in.
put signal to an equivalent time period and to transmit this
iime period to the display portion of the DMM.

1.23 Dual slope integration operates as follows in a

sequence of program (PCM) states:

a. Signal Integration (KM-A). The integrator capaci-

tor charges to a voltage proportional to the input

voltage during a 20 msec sampling period.

b. Reference Integrate (KM-C). During this period,

the integrator capacitor discharges at a constant cur­rent. The time that the integrator requires to dis­charge (full discharge detected by the Null Detector)
is measured by the counter. The data in the counter
at the end of PCM.C is proportional to the input
voltage.

1.28 The Function Switching board is used only when

either or both of the options (AC and Ohms) are installed.

With no options installed, the Function Switching board is

replaced with the Switching Bypass board. The Switching
Bypass merely connects the + Input (from input connector)
directly to the Isolator input and the - Input to ground.

1.29 At the rear edge of the Logic and Interconnection
assembly is a PCB connector that extends to the rear panel
and serves as the BCD output connector 1201. If the

optional Remote Program board is installed, it is mounted

on stand-offs above the Logic and Interconnection board

with the PROGRAM INPUT connector (J202) available at

the rear panel above the BCD OUTPUT connector.

1.30 The POWER input connector 1203, the power trans­former, and power transistors for the power supply are

mounted on the rear panel of the instrument. Other power

supply components are mounted on the Logic and Inter-

connection assembly. Also mounted on the rear panel, in
addition to .I201 and 1202, is the rear INPUT connector
J204, the ANALOG OUTPUT connector and common, the

EXTernal REFerence connector and common, and the line

fuse F201,

1.31 A dimensional outline of the Model 5900 is shown

in tigure 1.2.

c. Strobe @CM-D). At this time, data in the counter

is strobed into the storage latches and displayed -

the print pulse is inhibited, however if an uprange
or downrange command is generated by the Auto­range logic. If a range change is required, the

counter is reset and the program returns to PGM-A.

d. Reset @‘CM-E). At PCM-E, all internal logic is reset

in preparation for the next reading.

1.24 An additional control state, PGM.B, occurs after
PGM-A and is a delay to allow for propagation time of the
counter.

1.25 The Control/Display section generates the control
signals necessary to operate the signal conditioning and
integrating circuits.

1.26 MECHANICAL DESCRIPTION.

1.21 The ohms measurement option consists of a single
printed-circuit board. The AC options both consist of two
boards. The accessory boards plus the Digitizer, Isolator,

and Function Switching board all plug into the Main Logic

board called the Logic and Interconnection assembly. This

board also carries much of the instrument logic.

Figure 1.2 Dimensions

1.32 SPECIFICATIONS.

1.33 Specifications are listed in table 1.2.

1-3

980453

Table 1.2 - Specifications

SPECIFICATIONS, MODEL SSOO

AS A DC VOLTMETER IBASIC INSTRUMENTl

RATIO tdcldc. mVldc. acldc)

SPECIFICATIONS CONTINUED NEXT PAOE

Table 1.2 -Specifications (continued)

980453

l-5

SECTION 2

2.1 UNPACKING AND INSPECTION.

INSTALLATION & OPERATION

2.2
plastic-foam form within a cardboard carton for shipment.
The plastic form holds the DMM securely in the carton and
absorbs any reasonable external shock normally encountered
in transit. Prior to unpacking, examine the exterior of the
shipping carton for any signs of damage. Carefully remove
the DMM from the carton and inspect the exterior of the
instrument for any signs of damage. If damage is found,
notify the carrier immediately.

2.3 Included with the instrument in the packing con­tainer are the instruction manual, power cord, and rear in­put and BCD output mating connectors. With instruments
equipped with remote programming, a mating connector
for that accessory is included.

2.4 BENCH OPERATION.

2.5 Each Model 5900 is equipped with a tilt bail or
“kickstand” to enable the front of the instrument to be
elevated for convenient bench use. The tilt bail is attached
to the two front supporting “feet” at the bottom of the
instrument. For use, the bail is pulled down to its sup­porting position.

The Model 5900 DMM is packed in a molded

2.6 RACK MOUNTING.

2.1 The instrument can be mounted in a standard 19.
inch rack with the optional rack-mounting flanges (403402,
includes attaching hardware). To install the flanges, pro­ceed as follows:

a. With instrument on its side, remove four Phillips-

head screws holding bottom cover. Remove cover.
Remove screws holding feet (and bail) in place. Re­place bottom cover.

b. Place one of the supplied screws through each of

the two holes in the mounting flange (figure 2.1).

Thread a securing nut onto each screw just enough

to attach it to the screw (approximately one turn).

c. Place the mounting flange onto the mounting slot

in the instrument side panel so that the securing
nuts fit entirely into the slot. Be sure the rack­mount slots on the flange are toward the front of
the instrument.

d. Tighten screws. The securing nuts will rotate and

hold the flange securely in place.

2.6 POWER CONNECTIONS.

2.9 Standard units operate on either 1 IS volts or 230
volts, SO to 60 Hz (400 Hz available). Power consumption
is less than 40 watts. Operation on either of the two line
voltages is selectable by a slide switch on the rear panel.
Operation on lOO/ZOO volts or 1201240 volts is possible by
simple rewiring of the power transformer secondary wires:

WARNING
Disconnect the instrument from the AC Power source
before attempting to change power connections.
Potentially lethal voltages are exposed when covers
are removed.

a. For operation on 100/200 volts, cut the brown wire

1” from the transformer and splice it to the red
wire on the transformer; cut the blue wire 1” from
the transformer and splice it to the violet wire.

b. For operation on 120/240 volts, cut the brown

wire 1” from the transformer and splice it to the
black wire; cut the blue wire and splice it to the
yellow wire on the transformer.

2-I

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2.10 A standard power cable having a three-pin plug is
supplied with the instrument. It connects to POWER con.
nectar 5203. The ground pin (round) is attached to the

instrument case. It is important that this pin be connected

to a good quality earth ground.

2.1 I

Fuse receptacle F20l on the rear panel is equipped

with a .5 amp fuse in domestic units.

2.12 INPUT/OUTPUT CABLING.

2.13 Binding Posts.

2.14 Several connectors on the Model 5900 consist of a
pair of binding posts spaced so as to accept standard
“banana” plugs. The connectors are:

I

Front Panel

I

Rear Panel

+ INPUT f. ANALOG OUTPUT

+ OHMS CURRENT

?1 REFerence INput

2.15 Input cables to fit this type of connector can be
ordered from Keithley (P/N 5900-402190). Figure 2.2 is a
wiring diagram of this cable included for assistance to users
desiring to construct their own cables.

panel binding posts. The rear-panel input lines are wired in
parallel with the front-panel input lines. It is recommended
that the cable for the mating connector be constructed as
shown in figure 2.3 using two two-conductor shielded
cables. Other configurations may be desirable depending
on the ohms measuring method to be used (see para­graph 2.28).

I

2.18 MANUAL OPERATION.

2.19 Controls.

2.16 Rear Input Connector.

2.17 Instruments equipped with the -I or -IS rear input
option are supplied with 5204 7.pin input connector

(Keithley P/N 5900-600673) and a mating connector

(Keithley P/N 5900-600616). The instrument acceptsinputs

applied to this connector or inputs applied to the front-

2.20 All operating controls are located on the front panel
of the instrument. They are shown in figure 2.5 and their
operation described in table 2.1. Description of Systems
operation begins in paragraph 2.44.

2.21 DISPLAY.

2.22 The Pisplay consists of 6 LED decimal readout
devices with moving decimal point. The decimal point

moves in conjunction with the range switchor automatically

in auto range. Maximum usable readout with overrange is

159999. Overload is indicated by a NO and 160000 read­out. A non-compatible range and function is indicated by
a NO. However, mechanical interlocks are provided to pre­vent illegal combinations from the front panel. Figure 2.4
illustrates the readout, NO indicator, polarity sign and the

DC MO

+

r /--- r-7 ,---I ,---I ,--1 AC

- I L-, L-4 L-4 L-,’ L-4 PGM
NO,’ --J. ,’

Fiwe 2.4 . Readout

: : :

KO

n

FIL R

2-2

Figure 2.5 -Front Panel

Table 2.1 . Operating Controls

Control

POW1

(rocker switch)

Function Select

(rotary switch)

Range Select
(rotary switch)

DATA OUTPUT
(pushbutton)

Position

ON (UP)
OFF (down)

ACT

DC

AUTO

Other Positions

Depressed

Function

Applies power to instrument

Removes power from instrument

Selects the measurement of AC voltages on the I, IO, 100, and

1000 volt ranges (max. input, 1OOOV RMS)

Selects the measurement of DC voltages on the .l, 1, IO, 100,
and 1000 volt ranges (max. input, IlOOV)

Selects the measurement of resistance on the 10 ohm range; on
the.1,1,10,100,andlOOOkilohmsranges;oronthe10or100
Megohm ranges

Selects Auto Range in which the optimum range is selected auto­matically by internal circuits. Uprange occurs at 160% of full
scale; downrange occurs at 15% of full scale

Enables manual selection of fiied ranges. Ranges permissible for
each function are inscribed on the parlel

,Enables the print pulse causing BCD data at P201 to be recorded

by printer, or other output device. (Output data is present at
P201 regardless of the position of this switch.)

PROGRAM CONTROL
(pushbutton)

Depressed

Enables the selection of range, function, and mode to be made
externally through the remote programming connector and dis.
ables all front panel controls (requires programming option)

RATIO
(pushbutton)

Depressed

Selects a ratio measurement in which the readout represents the
ratio of the input to an external d-c reference voltage (applied at

terminals on the rear panel) multiplied by 10: Ein/ERafx 10

FILTER

Depressed

Adds an active four.pole filter across the input circuit

(pushbutton)

RATE EXT (ccw)

(pot)

cw

FRONT/REAR FRONT

Selects the Hold mode. A new reading is initiated through the
remote program input

Increase periodic read rate to a maximum of four readings/second

Connects front panel data input terminals to instrument

(slide switch)

REAR

Connects rear panel data input terminals to instrument

*NOTE: Ohms input terminals are open in AC or DC function.

TNOTE: For inputs greater than lSOV, Filter should be “IN”.

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2.23 MEASUREMENT CONNECTIONS.

NOTE

Before taking any measurements, refer, to the list of
maximum input voltages, table 2.2.

Table 2.2 - hlaximum Input Voltage

CAUTION

Do not exceed the following maximum inputs:

DC

AC

1lOOVDCor 1OOOVRMSAC

1OOOV RMS decreasihg to 20V RMS at

1 MHz (see figure 2.7)

n

+SOOV peak between +I and -I(lOOOV
RMS if in DC or AC function.)

RATIO

Input: same as function selected

Reference: +lO.SV, -0.5V

achieved by ‘placing a shorting bar between - INPUT and
GUARD and shorting the single banana plug (shield) to the

-

INPUT side of the double banana plug at the input con­nector. This arrangement is adequate for measuring all but
low voltage (mV) levels and/or in high-noise environments.

2.27 When making “floating”voltage measurements(both
measurement points above ground potential), do not con­nect GUARD to measurement ground without making sure
that the voltage between GUARD and - INPUT does not
exceed 250 volts.

Y

‘RMS

GUARD

Voltage between GUARD and - INPUl
must not exceed 250 volts or damage
to the instrument may result

2.24 Basic Voltage Measurement.

2.25 An ac or dc voltage measurement connection rec­ommended to minimize the effects of noise requires a two­conductor shielded cable connected as shown in figure 2.6.

t

Figure 2.6. Basic Voltage Measurement Connections

2.26 For all voltage measurements, the GUARD lead ar

Id
the - INPUT lead are connected to the measurement point
nearest ground potential.

Somewhat less shielding is

2.28 Ohms Measurement.

2.29

Ohms measurement in the Model 5900 consists of
the application of a known current through the unknown
resistance (Rx) and measuring the ratio of the voltage drop
across Rx to the drop across an internal “full-scale” resistor
(Eh/EFS). Current through Rx is applied through leads
from the f. OHMS CURRENT terminals. The voltage drop

is sensed by the + INPUT terminals.

2.30 TWO.WIRE MEASUREMENTS.

2.31

Connections for a simple two-wire shielded ohms

measurement are shown in figure 2.8a. It consists simply of
a single-conductor shielded cable with the conductor serving
as both the t CURRENT and + INPUT leads and the shield

2.4

(4

(b)

Y&v453

lNP”T CVRRENT

Figure 2.8 - Two Wire Ohms Measurements

RX

2-s

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2-6

Figure 2.9 - Four Wire Ohms Measurement

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carrying - CURRENT and - INPUT. While reasonably
accurate measurements can be made with this method,

shunt leakage problems result from the parallel combinations

of Rx and the cable impedance. This causes loss of accuracy,
especially at high resistance (100 Ma range). Also, lead
resistance becomes a factor in the 10 and 100 ohms ranges;

the four wire measurement system is recommended for

these ranges.

2.32 A more accurate two-wire measurement connection

is shown in figure 2.6b. The + INPUT and + CURRENT,

-

INPUT and - CURRENT terminals are again tied to-

gether. But now, the positive side is a single-conductor,

shielded cable with the shield tied to Ohms Guard. Ohms

Guard is the low ANALOG OUTPUT terminal on the rear

panel of the Model 5900 when ohms is selected. The negative
side is a single wire connected as shown. Guard current is
present in the low side, but the leakage problems of the
first configuration are eliminated.

2.33 In high noise-level environments, the configuration
shown in figure 2.8~ is recommended. This method also

eliminates error due to shunt leakage, but provides more

complete shielding. The positive terminals are tied together
and carried in a single-conductor, double-shielded cable with

the inner shield tied to OhmsGuard (-ANALOG OUTPUT).

The outer shield is tied to GUARD. The negative terminals

are tied together and carried in a single-conductor shielded
cable with the shield tied to GUARD. This configuration
eliminates guard current sensitivity, thereby increasing
guarding characteristics.

2.36 This configuration, although shielded, places the
shield capacitance and cable leakage in parallel with Rx.

This results in loss of accuracy and slow measurements. In

addition, it is very responsive to the triboelectric effect at
high resistance measurements.

2.39 Better guarding is achieved by the use of the con­figuration shown in figure 2.9b. Here again, RG196U teflon
dielectric cable (either single-conductor shielded or two­conductor shielded) is used on the positive terminals. The
shield(s) are connected to Ohms Guard (low ANALOG
OUTPUT terminal). The negative leads are single wires with
the - INPUT terminal tied to GUARD.

2.40 This eliminates much of the shunt leakage problem

of the previous configuration since guard current now flows

through the low side of the measurement circuit. Measure­ment is much faster since the shield capacity is driven by
the guard current.

2.41 A high-noise environment calls for the “super”
configuration shown in figure 2.9~. Here, a two-conductor,
double-shielded cable is used as the positive leads. The inner
shield is tied to Ohms Guard. A twoanductor shielded
cable is used as the negative leads. Its shield is tied to
GUARD and to the outer shield of the positive cable. The

shield is also tied to CURRENT at the measurement point.
This configuration maintains high guarding characteristics
while eliminating guard current sensitivity.

2.42 Ratio Measurements.

2.34 FOUR-WIRE MEASUREMENTS

2.35 In most system applications, the device to be meas­ured is located at B remote location requiring interconnection
by cables of lengths from several to possibly hundreds of
feet. When measuring low resistance values over long cables,
most lead resistance problems can be solved by the use of a
four-wire measurement system.

2.36 For high resistance measurements over long cables,
other problems are encountered: noise pick-up, leakage
resistance, and capacitive loading of the system. These
problems can be minimized by proper shielding and the use
of ohms guard.

2.37 Figure 2.9a shows a basic shielded four-wire ohms
measurement configuration. This method uses two single­conductor shielded teflon cables. The conductors carry the
positive sides of the INPUT and CURRENT lines while each
shield carries the low side.

2.43 Ratio measurements are made by applying a positive

d-c voltage to the reference input terminals on the rear panel

and an input signal of any function at the front input
terminals. For DC/DC or AC/DC ratios, the reference

voltage must be within the range of +IV to +lO.SV. Input

signal limitations (numerator) are the same as tbosc given
for conventional measurement of the particular function

(table 2.2). The readout is the ratio multiplied by ten:

Einput/Ereference x 10. In the standard instrument the

INPUT terminal is internally connected to the REF in­put terminal; in instruments equipped with the option 62
4-wire ratio, both reference inputs arc floating (IO Ma
between - REF and -SIGNAL).

2.44 SYSTEM CAPABILITIES.

2.45 The 5900 has two system interface connectorsdesig­nated as 3201 (PRINTER OUTPUT) and 5202 (PROGRAM
INPUT) mounted on the rear panel of the instrument (fig
ure 2.10). The following is a brief description of the capa­bilities of each connector.

2-7

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Printer Output - 5201.

2.46

2.47 Through this connector the 5900 supplies BCD
representations of the decimal display; various flags or
indicators of the mode of operation, function and range;
and a print command. Provision has also been made for 60
Hz instruments to accept a fast (20 readings per second
maximum) or a superfast (I 01 readings per second minimum)
read command. In 50 Hz units, the fast command obtains

I7 readings per second, minimum, and the superfast com-

mand 93 readings per second.

2.48 Program Input.

2.49

Through this connector the 5900 receives externally
generated signals that select the function, range, mode of
operation, and initiate the read commands.

2.50 LOGIC LEVELS AND ELECTRONIC IN-

TERFACE.

TTL-compatible positive-true logic levels are used

2.5 1
in the 5900. In some instances, however, complementary
signals are used. These terms are more specifically defined
below:

other words, the complement of X is x. The truth table
shows that the two signals X and x, are by definition, in
opposite logic states (see table 2.3).

Table 2.3 - Positive True Logic Relationships

Voltage Level of

Voltage Level of

Signal Logic State Output Line “x” Output Line “p

“X” True or “1” 2.4 - 5.0

False or “0” 1 0.0-0.4

2.53

As seen above, if gate A has a true or “1” level on

Volts 0.0.0.4
Volts 1

2.4.5.0

output X, its voltage level is the most positive of the two
ranges present, and output x must be in a false or “0”
state with the lowest or most negative voltage range present.

The reverse would be true for a false or “0” level on output

X.

2.54 Driving the Inputs.

2.55 All inputs are TTL compatible and most are the
equivalent of one 7400 series TTL input with a pull-up
resistor for contact closure operation.

Signals and Their Complements -

2.52

If the non-inverting output of gate A is defined as

signal X, then it follows that the inverting output is ???; in

Figure 2. IO - Rear Panel

0

2.56 TTL Loading Conditions,

2.57 To input a “I” level the pull.up resistor will supply

the necessary source current (40 /.tA) to maintain the mini­mum 2.4 volts. In fact, the pull-up resistor will maintain a

2-8

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Figure 2.11 Measurement Sequence

2-9

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one level as long as the input source resistance (RI) to

ground is greater than ISK ohms.

2.58 To input a “0” level, at least 2.0 ma of current must
be sinked maintaining the input voltage below 0.4 volts.
This requires a resistance to ground of 200 ohms or less.

Exceptions to Input Loading Conditions.

2.59
a.

Program Storage Input (5202, pin B.15) is the
equivalent of 3 TTL inputs and requires a minimum

5.8 ma sinking current, or 68 ohms or less to com­mon.

b.

Maximum input voltage level, referenced to common,
must not exceed 5.5 volts peak. Otherwise, gate
destruction will occur.

c.

The Direct and Time Out Commands are AC coupled

with pullap resistors to t5 volts. These inputs are
compatible with TTL outputs or contact closures
to ground. The AC coupling does require that rise
and fall times be less than 100 peconds. This input
circuit is illustrated below:

ts” +5V

P 9

2.62 Timing Sequence.

2.63 The standard remote mode of operation of the 5900
is to initiate a reading sequence with each Direct Command
received through the programmer, providing
time has been allowed between commands for the reading
to be completed. This reading sequence is illustrated in
figure 2. I I

TI .To

T2-TI

T3-T2

T4.T3

During this period the input signal must fin­ish settling to within the desired accuracy.
Any control changes involving the 25 msec
relay settling time (a) can he completed;
other logic control inputs (b) can also be
changed.

The Direct Comma signal, which is AC

coupled, must meet the following conditions:
a. Rise and fall times less than 100 /.wc.
b.

Signal must stay in the logical “0”
state for at least 3.4 /&ec. If these
conditions are met, the internal read
command is sustained at T2 and the
signal integrate period is started.

The period of signal integration lasts for

16.2/3 mw (60 Hz line frequency; 20 mw
in 50 Hz units). During this time the inte­grator charges to a voltage proportional to
the input voltage. This is the input sampling
period.

During this period, the integrator is isolated
from the input signal, and is discharged at a.

precise current. The time the integrator re­quires to discharge to a level equal to its
voltage at T2 is proportional to the input
voltage. This time is measured by an internal
counter and stored.

that

sufficient

d. Digital output common can be floated as high as

200 VDC above power line ground.

2.60. TTL Output Capabilities.

2.61 The 5900 electrical outputs are specified to drive
two ‘ITL inputs such as described in the TTL loading section.
Summary:

False: 0 to tO.4V
True: t2.4 to +S.OV
Fanout: 2minimum ,
Maximum Capacitance Load: 500 pF

2-10

T5.T4

To-TS

TI -To

This I.7 /J.W period is required to strobe the

new reading from the internal counter into
the readout latches.

This 5 mseconds (&IO%) is required to reset

the internal logic for the next reading.

If the next read command is a Direct
Command, this period must be made long
enough to allow for the condition covered in
the first cycle; however, if the next command
is a Timeout Command, this period can
approach zero since the necessary timeout to
satisfy these conditions are automatically
programmed.

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Figure 2.12. Command Timing

2.64 Other Read Command Options.

2.65 In addition to the Direct Command, there are two
other programmable read commands, as illustrated in fig­ure 2.12.

a.

Time Out Command: Again, this is an AC coupled

input which must have rise and fall times of less
than 100 weconds but must remain in a “0” state
for at least 0.1 @second. The timeouts given in
table 2.7 for various combinatioris of ranges and
functions ranging from 30 mseconds to 500 msec.
onds will be automatically inserted before the in­ternal read command is generated. If this command

is wired to the m on J2Ol - pin
All, fully automatic reading with timeouts is
achieved.

The 5 msec internal delay is not adequate for settling
time on the 100 VDC, 1000 Ka 10 MS1, IO0 MS1
ranges, or any AC range. Therefore, the timeout com­mand, providing timeout delays listed in table 2.7,
must be used to initiate accurate readings on these
ranges unless a fixed range and function have been
programmed and the input has been present longer
than the timeout period.

System Direct Command: While the other two read

b.

commands were AC coupled and programmed

through the Program Input Connector (J202), this
command is DC coupled and programmed through

2-11

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Figure 2.13. Minimum Read Rate vs. Input

the Printer Output Connector (5201). The $&%
Direct Command must remain in the “0” state for
at least 3.4 /.&seconds to generate the internal read
command. This delay, as in the Direct Command, is and internal reset remain fixed while the reference integrate
to prevent noise from triggering the readings. If this period can vary from 0 to 32 mseconds. Therefore the
command is tied to ground, the 5900 will recycle at maximum read rate could very from 17.4 to 45 reading per
its maximum reading rate with no timeouts. second.

2.66 Reading Rates.

2.67 In figure 2.13, integrator operation with three dif­ferent input signal levels is illustrated: half scale, full scale,

2-12

and 160% of full scale (full scale is defined as 100000 on any
range). The figure shows that the maximum reading rate is
a function of the input signal. The signal integrate period

2.66 Superfast.

2.69 The Superfast reading mode (programmed through

either the PRINTER OUT or PROGRAM INPUT connector)

980453

Figure 2.14

- Superfast

increases the minimum reading rate from 20.5 to 102
readings per second (50 Hz: 17.4 to 93 r/s). This is done at
the expense of losing the least-significant digit which is re­set to zero (blanked out on readout). The signal integration
period is reduced from 16.2/3 msec to I -2/3 msec (SO Hz:

20

msec to 2 msec). This and the resulting reference inte­grate period reduce the maximum recycle time from 48.8
msec to 9.8 msec (SO Hz: 57.5 msec to 10.7 msec), thereby
yielding the 107 reading per second figure (93 r/s with 50
Hz). Timing changes are shown in figure 2.14.

2.70 PRINTER OUTPUT.

2.71 The printer output connector is a double-edged

PCB connector (extension of Interconnection and Logic

board) with pins Al through A22 on the bottom edge and

pins B I through B22 on the top edge. Pin assignments are
shown in figure 2.15. All outputs are referenced to digital
ground pin B I.

Read Rate (Worst Case)

2.72 Numerical Data

2.73 Numerical data appears as positive true, four-line
BCD code, as shown in figure 2.15. The designator of each
line identifies the digit and weight. For example: Pins Al8,

19, 20, and 21 are designated 12. Ig, 14. and I, consecu­tively. The 1 indicates these lines correspond to the units
or least significant display; the 2, 8, 4, and I subscripts
indicate the hinary weight of each line.

CAUTION

True output lines arc not short-circuit proof. Acci­dental grounding may damage the output circuitry.

2.13

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Figure 2.15 . Pin Assignments 5201 PRINT.!?R OUT

2.74

Polarity is indicated in positive true format on pin
A9 (positive) and pin A10 (negative). The positive polarity
line is true when the function output is AC or .lK through

IK OHMS ranges. Negative polarity is true with Ohms on
the IOK through lOOMranges. If the instrument overranges,
the polarity bit is not updated since no axis-crossing has
occurred.

2.76 Function Data.

2.76

Function outputs appear on pins Al, 2, 3 and B2 in

their true format. For example: with AC function selected,

2-14

AC is true and is indicated by B true level on the corre­sponding line.

2.77 Range Data.

2.78

Range data appears in four-line BCD code on pins

Al4 through Al7. Range codes are described in table 2.4.

2.79 “NO” Indication.

2.80 The NO line (pin AI2) is the same as the
NO indicator on the readout. The line is true if a function

Table 2.4 - Range Codes (Printer Output)

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or range is selected for which the particular instrument is
not equipped. Overrange is indicated by a true NO line plus
a numerical data output of 160000.

2.81 Status Output Lines.

2.82 The following outputs indicate the status of the

conversion process within the instrument.

DATA READY. This line (pin Al 1) remains true
during the signal and reference integration periods
plus any overrange time, if required. The line drops
to the false level to indicate to the printer that the
measurement is complete and output data can be
printed (PrinterCommand). With front-panel opera­tion, DATA READY ‘is enabled only when the

DATA OUTPUT switch (on front panel) is de-

pressed. Minimum false level time is 4.5 mseconds.
HOLD FLAG. A true level on this line (pin A4)

indicates that the instrument is in the Hold mode.
A reading can be initiated by one of the following
commands:

SYSTEM DIRECT COMMAND (J201.A8)

1.

2. bIRECT COMMAND (3202.A15)

d.

SIGNAL INTEGRATE. This line (pin B 1 I) becomes
true at the end of the signal integration period. After
this time, the input signals may be changed in prepa-

ration for the next reading. The input signal need
remain constant only while the instrument is in
Signal Integrate, indicated by this line in the false
state. For example, the l-2/3 msec sample time in
Superfast could be used in slow sample and hold
applications.

2.83

Input Control Lines.

a.

DATA DISABLE. A contact closure to ground or a

false logic level applied to this line (pin A7) inhibits
the DATA READY output (Print) pulse.

SYSTEM CONTROL. A contact closure to ground

b.

or a false logic level on this line (pin B6) &sables

all front panel operating controls. Operation of the
instrument is then under control of the Remote
Program input. This command duplicates operation

of the PROGRAM CONTROL switch on the front
panel. It is necessary that one of these commands
be initiated during Autorange to inhibit extraDATA

READY pulses.

TIMEOUT COMMAND (JZOZ-B IO)

3.
RATE Control (front panel)

4.

SYSTEM READY. This line (pin AS) drops to a
false level to indicate that the instrument can now
initiate a new reading at the first available read com-

mand.

c.

SUPERFAST. A contact closure to ground or a
false logic level applied to this line (J20l-A6 or

1202.A7) decreases the conversion time of the
instrument while sacrificing the least-significant

digit. This mode is described in paragraph 2.68.
Because of the superfast read rate, do not use this
mode with Autorange.

Z-15

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r

Figure 2.16 -Pin Assignments 5202 PROGRAM INPUT

2.84 SYSTEM DIRECT COMMAND.

2.85 To externally initiate a measurement with this com­mand, the instrument must be in the Hold mode. Then, a
contact closure to ground or a false logic level to this line
(pin A8) generates a read command. Minimum false level

time is 3.4 r.oec. Continuous readings at the maximum read
rate are obtained by tying this line to ground. Read com-

mands delayed by 5 msec f 10% (for settling time) are then
generated automatically.

2.86 REMOTE PROGRAMMING.

2.87 The instrument accepts commands made through
PROGRAM INPUT connector J202 on the rear panel. Pin
assignments of 5202 are shown in figure 2.16. Commands

2-16

are made by a switch closure from the appropriate pin to
ground or by standard TTL logic levels as described earlier.

2.88 SYSTEM CONTROL.

2.89

A contact closure to ground or a false logic level
applied to pin 86 disables all front panel operating controls.
Operation of the instrument is then under control of the

remote program input. This line duplicates the PROGRAM
CONTROL switch on the front panel.

2.90 Function Programming.

2.91 The desired function is selected by applying a

ground or false logic level to the appropriate pin (table 2.5).

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Table 2.5 -Function Programming

FE

I

2.92

settling time on the 100 VDC, 1000 Kilohm, IO Megohm,

100 Megohm, and all AC ranges. Therefore, the timeout

command, providing timeout delays listed in table 2.7, must
be used to initiate readings on these ranges unless the input
is fixed with range and function predetermined.

2.93 Range Programming.

2.94 Range programming is selected by applying false

logic levels in BCD code to the four range lines described in

table 2.6 below. With no lines programmed, Autorange is
automatically selected.

2.95 + Five Volts.

z

OHMS pin A9

RATIO
FILTER pin B7

The 5 msecond internal delay is not adequate for

I

NC
nin A8

pin 88

2.99 Read Commands.

2.100 Either of two read command lines can be selected
by a contact closure to ground or by a negative logic

level applied to the appropriate pin. Pin AIS, DIRECT
COMMAND, commands a new measurement if applied after
a five millisecond reset delay, and if the command is pre­sent for 3.4 peconds. Pin BIO, TIMEOUT COMMAND,
starts a new measurement after five milliseconds plus a
timeout delay to allow for internal settling time of the
measured signal. TIMEOUT COMMAND may be com­manded before the previous 5 mw delay since the timeout

generator stores the reading.

2.101 Timeouts.

2.102 Timeout periods for each function are listed in
table 2.7. In Autorange, the indicated delays are taken

following each range change.

2.103 Data Inhibit.

2.104 A contact closure or false logic level on pin B9
inhibits DATA READY OUTPUT (Print pulse) from being

generated.

This voltage, +5 volts + 5%, from the logic power

2.96

supply isavailable at pin Al3 for external use. Current out­put is .lA, maximum.

2.97 Hold.

2.98
position of the front panel RATE potentiometer and is
selected by a contact closure or a false logic level on pin

commands.

The Hold line parallels the operation of the ccw

Hold is required when using either of the two read

AIO.

Table 2.6 _ Range Codes (Rogrammer)

2.105 Program Storage.

2.106 A false level (equivalent to three TTL inputs) on

pin BIS will stoIe all the programmed inputs except the
Direct and Timeout commands as they existed on the

negative edge of this command (see diagram below).

PROGRAM STORAGE

c’

at this time the program
is stored

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2.107 SUPERFAST. 2.109 ADDING/REMOVING ACCESSORIES.

2.108 A contact cloture to ground or a false logic level

applied to pin A7 decreases the signal integrate and the
reference integrate times (see paragraph 2.68). This pro­vides the maximum reading rate in the Direct COMMAND

mode of operation. Because of the high reading rate, Supa­fast

must

be programmed with a fixed range rather than

AUTORANGE.

Table 2.7 . Timeouts

DC

I Ohm to I Meaohm 130 msec

IO Meg*

100 Megohm

Filter

30 rmec

1

30 msec
300 msec
470 msec (plus function timeout)

ACffixed rawznofilter) 180 msec

AC+Filter(&Autorange) 650 msec

*Use filter for <.Ol%

error

I

Table 2.8 -Maximum Input Voltage

CAUTION

Do not exceed the following maximum inputs.

2.110 The AC and Ohms options may be added or re­moved at any time in the field without modification to the
basic instrument. Note that the switching board (403625)
is required whenever the plug-in options are used. Access

to the mounting connectors is by removal of the top cover,
held down by captive screw in each of the four corners,
and by removal of the shield, mounted by four flat head
screws.

2.1 I I When an option is added or removed from the

instrument, a jumper corresponding to the option is re­moved or added to allow proper operation of the NO cir-

cuitry. The two jumpers (WI Ohms and W2 AC) are
located on the display board, shown partially in figure 2.17.
When an option is added, the corresponding jumper is

added; conversely, whw iin wxcssory is removed, the

jumper is rcmovcd

DC

1000 MC or RMS AC

All ranges

AC

1000 RMS to 20 kHz decreasing 20 dB/

decade to 20V RMS at 1 MHz

RATIO Input: same as function selected

Rcfercnce: +10.5V. -0.5V

) OHMS ) +5OOV DC or Peak AC

GIJARD Voltage between GUARD AND - INPUT

mutt not exceed 250 volts or damage

1

1 / to the instrument may result

Figure 2. I7 - Jumper Location

2.18

SECTION 3

3.1 GENERAL.

3.2 This section contains procedures that compare the
operation of the instrument against the published specifi­cations found at the front of this manual. It is intended to
be used for incoming inspection and as a periodic check
determine if recalibration of the instrument is warranted.

3.3
proper operation and that the instrument is within the 90
day accuracy limits. Covers of the instrument are not re-

moved for any of the tests.

temperature of the environment is 23” + 5°C.

3.4 REQUIRED EQUIPMENT.

3.5
checking the instrument. The equipment in this table, with

The procedures provide sufficient checks to verify

The required ambient

In Table 3.1 is a list of equipment necessary for

Table 3.1 - Required Equipment

to

SPECIFICATION TESTS

the exception of those in the OTHER category, is the same

as required for recalibration and is explained in detail in

Section 5.

3.6 PROCEDURE.

3.7
ment end the test equipment as shown in the figure supplied
with each accuracy check. Select the controls and inputs as
called out in the tables and monitor the instrument readout
for the indicated values. If the instrument is equipped
with the rear panel selectable input option, set the FRONT/
REAR switch to the FRONT position for all procedures
presented in this section

Allow one hour for warmup. Convert the instru-

ES1 SRI with corrections
ES1 SRl with corrections
ES1 SRI with corrections
ES1 SRI with corrections
ES1 SRI with corrections

ES1 SRI with corrections

DVM INPUT SIGNAL

FUNCTION

Table 3.2. DC Range Check (Low Ranges)

DC

RANGE VOLTAGE

STANDARD

DIVIDER
SETTING

NOMINAL

READING

TOLERANCE

NOTE

DC

.lV I0.00000

IV 10.00000

STANDARD CELL

.01000 .1ooooo .099992 - .I00008
.10000 I .ooooo

0.99997 - 1.00003

(1” VOLT SOVRCE,

23% + PC
(After zeroing)

Table 3.3 - DC Range’Check (High Ranges)

( “fooooo

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+

3-3

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Table 3.4 -3.Wire Ratio Check

TOLERANCE

Table 3.5 -4-Wire Ratio Check

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DVM

FUNCTION

DC
RATIO

I

INPUT SIGNAL

RANGE “OLYAGE

STANDARD

10

10

+ 2.ooooov
+ 1 o.ooooov

-1o.ooooov

I

NOMINAL

READING

tlO.OOOO
+10.0000

+10.0000

I

TOLERANCE

9.9980

9.9996

9.9996

- 10.0020

-

- 10.0004

I

~O.OOO~

NOTE

23% + 5°C

(After zeroing)

3-5

I

980453

Table 3.6 - DC Input Resistance

TOLERANCE

*Adjust the DC Voltage

Standard to produce the
DVM DISPLAY reading.

l--+T-1-1

O”ARDTERMlNAL

STRAPPED TO LOW

lNP”T TERMINAL

DC “OLTAGE STANDARD

0000000

Table 3.7 - Model 33 AC Converter Range Check

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TOLERANCE

formation on use

3-7

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Table 3.8 - Model 32 AC Converter Range Check

DVM

FUNCTION

-__­AC

INPUT SIGNAL

IT111

0000000

3-8

L

0

0

0 0

c

0

ZACo 0 0

0

u

000

l_;i

I

i

Table 3.9. Ohms-Megohms Range Check

TOLERANCE

TOLERANCE

(Same as Standard)

3-9

Table 3.10 -Common Mode Rejection (In DC Volts Function)

TOLERANCE

DMM’s readout
in the “nominal

Table 3.11 - Normal Mode Noise Rejection (In DC Volts FuKtion)

DVM

FUNCTION RANGE

t

DC
FILT. OUT

FILT. IN

DC

IO osv
IV

0.w 2V*, 60 Hz?

INPUT SIGNAL

AC

iOV*, 60 Hz? 00.5000

*peak

t50 Hz (Option 04)

NOMINAL
READING

0.50000

TOLERANCE

~400 digits

? 2 digits

NOTE

3-1 I

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Table 3.12 _ Common Mode Rejection (In AC Volts Function)

TOLERANCE

NOTE

Enter reading with

shorted input in
nominal column
before beginning

3-12

SECTION 4

4.1 GENERAL,

4.2

This section describes the operation of the main
circuitry of the Model 5900 DVM, briefly covering the
mechanical organization and then the electrical operation of
the instrument. The simplified drawings provided in this
section are for the purpose of illustration, and supplement
the complete schematics of Section 6.

4.3 MECHANICAL DESCRIPTION.

4.4

The Model 5900, shown in figure 4.1, consists of a
large, single, printed circuit Logic and Interconnection
board (Main Logic) with as many as 12 separate PC boards
plugging directly or indirectly (by means of cables) into the
Main Logic board. The electronics are housed in a sturdy
die cast and stamped aluminum package with the readout,
input terminals, and allmanual controlslocated on the front
panel. On the back panel is located the power cable input,
all data output, optional remote input, analog output,
external reference, and optional rear inputs.

4.5 ELECTRICAL DESCRIPTION.

4.6

The instrument is divided into three functional
groups. These are the Signal Conditioning section, the

Analog-to-Digital Conversion section, and the Display/

Control Logic section.

by the options. The interconnection of the Switching board
with the options and the other components of the Signal
Conditioning section is shown in block diagram form in
figure 4.2.

4.12 The control of signal flow through the Switching
board, shown in simplified form in figure 4.3, is by means of
two relays Kl ‘and K2. The three possible signal routes

provided by the board are illustrated in figure 4.4. Re­ferring to this figure, with the- dc function selected,
neither of the relays is energized and the signal flow is as

shown in (a); with the ac functiowselected, relay Kl is

energized and the signal flow is as shown in(b); with ohms
function selected, relay K2 is energized and the signal flow
is as shown in (c).

4.13 The range control of the option boards uses analog

supply voltages and require isolation from the digital

supplies and decoding. This is provided on the Switching

board by three Optically Coupled Isolators (OCI) and a
BCD to TEN line driver. The decoding of the range logic is
given in table 4.1.

Table 4.1 -Switching Board Range Decode

4.7 SIGNAL CONDITIONING SECTION.

4.8

The Signal Conditioning section for a fully equipped

instrument consists of: the Switching Board, the Ohms

Converter, the Averaging AC Converter or the RMS AC
Converter, the Attenuator, and the Isolator. The basic
instrument consists of the Switching Bypass Board, the

Attenuator, and the Isolator.

4.9,

The Signal Conditioning section routes, scales, filters

and, when required, converts the input signal into a stable

lOvolt full scale dc level for use by the measurement portion

of the DVM.

4.10 Switching Board.

4.11 The Switching board is a single printed circuit
board and occupies conne&ors J5 and 36 on the Main Logic
board. The Switching board is used with instruments
equipped with either the Ohms Converter or either of the
available ac converters and is necessary for the generation
and isolation of range data and for signal routing required

4.14 Ohms Converter.

4.15 The Ohms Converter circuitry is mounted on a

single printed circuit board and occupies connector JIO on
the Main Logic board. The circuitry, shown simplified in
figure 4.5, consists of a high gain amplifier and a relay
operated positive current source that is capable of pro­ducing any one of eight precise current levels depending on
the range selected.

4-l

LOGIC AND
INTERCONNEC

READOUT

DISPLAY

TION

J2

J4

PROGRAM (LOCATION -

J3

BOARD NOT SHOWNI

I

Jl4 II-WIRE RATIO (LOCATION

BOARD NOT SHOWN)

J7 ATFENUATOR

J8 ISOLATOR

J9 DIGITIZER

JlO OHMS CONVERTER

‘INSTRUMENTSHOWN IS EOUIPPED~WITH RMSCONVERTER,

Figure 4.1 -M&mid Assenrbly

Jl, RMS BYPASS’ OR

AC CONVERTER

J12 RMS CONVERTER* OR

SCALtNG AMPLlFlER

980453

4.16 The Ohms Converter, in conjunction with the
Switching board, the Attenuator, and the Isolator, converts
the resistance to be measured into a proportional dc voltage
that can be measured by the DVM. The current produced
for each range, when applied to a resistance equal to the
range selected, generates a voltage et the output of the
resistance measurement network of 10 volts.

4.17 The resistance measurement network assumes two
forms, depending on the range being measured, as shown in
figure 4.6. The basic technique used consists of effectively
connecting the resistance to be measured (Rx) as a negative
feedback path of an operational amplifier, with the amplifier
provided by the Ohms Converter and the input to the
operational amplifier formed by the current generator. In

this hookup, the current through Rx equals the current
generated by the current SOIIIC~. Referring to configuration
(a). used for the ranges 10 kilohm through 100 megobm, the

voltage developed across Rx is monitored through the - IN

front panel connector and buffered by the isolator

in a

gain­of-one mode. The full scale output for these ranges, as
shown in the table, is -10 volts. Referring to figure (b),
the isolator is connected in a potentiometric configuration
but with the input at an effective ground potential and the
reference end of the feedback nehvork tied to the voltage

developed across Rx. The low impedance provided by the
isolator feedbacknetwork is offset by the current compensa-

tion circuit (CL). This circuit monitors the output potential
of the isolator and produces a current drain precisely equal
to the current produced by the feedback network. The re­sult is that the feedback network appears to have an

extremely high input impedance. The configuration used

in (b) reduces normal the gain of the isolator by I, thereby
producing gains of 99 and 9 as shown in the table.

4.18 Scaling Amplifier.

4.19 The Scaling Amplifier, shown simplified in fig
ure 4.7, is used in conjunction with the Averaging AC

Converter and occupies position J12. It provides isolation

between the signal being measured end the signal converting

circuitry and it scales the input signal to a level suitable for
the converter (1V RMS output for a full scale input).

4.20 The Scaling Amplifier consists of an AC coupled
operational amplifier with four possible gain settings (XI,

X.1, X.01, and X.001). The gain control network is con-

trolled by three relays and these are operated from decoded
data from the range logic. A change in the roll off of the
amplifier is provided when the 1 volt range is selected.

4.3

980453

4-4

Figure 4.3. Switching Board

la) DC Routing

P6

.1v + 1” ,+ INPUT,

H

, .I + 1” ,- INPUT,

6 0

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0

0

K1

lb) AC Routing

c) Ll Routing

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*

I

4-6

Figure 4.5 - Ohms Converter

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Figure 4.7 - Scaling Amplifier

4-8

Figure 4.8 _ Averaging AC Converter

YKfJ453

4.21 Averaging AC Converter.

4.22 The Averaging AC Converter receives the scaled in­put from the Scaling Amplifier and generates a positive dc

equivalent for the DVM, measurement section. The circuitry
is mounted on a single printed circuit board and occupies
location 111 on the Main Logic board. The circuitry, shown
simplified in figure 4.8, consists of an active rectifier, a
summing qmplifier, and an active filter circuit.

4.23 Referring to figure 4.8, a full scale input (1.414
volts peak) is shown applied to the input of the active
rectifier. The active rectifier consists of an operational
amplifier having two polarity selective feedback loops (one
positive, one negative), and the closed loop gain of the
circuits is set at 2. The output of the negative going feed­back loop is fed through a resistor to the summing node of

the summing amplifier. Also fed to this summing node and
through a resistor is the full wave input signal. The
summing amplifier adds the two inputs, averages them and
multiplies the signal by I .I I to produce the dc equivalent
of the RMS input, or 1 volt dc. The ripple content is
attenuated by the summing amplifier. A full scale input of

100 Hz would result in a ripple at the summing amplifier
output of 350 millivolts. Further ripple attenuation is
provided by the active 3.pole filter. For the same example,
the filter would increase the ripple attenuation to=5 milli-

volts.

4.24 RMS AC Converter.

4.25 The circuitry is shown simplified in figure 4.9. The
Scaling Amplifier consists of an operational amplifier with
a fixed input impedance and four feedback paths. The
feedback path for the one volt range is permanently wired
into the circuit; the 10, 100, and 1000 volt range feedback
paths are connected in parallel to the I volt feedback path
by relays KI, K2, and K3. The scaling amplifier supplies an
accurate 1 volt output on each range selected with full
range inputs applied.

4.26 The active rectifier is an operational amplifier with

two polarity selective feedback paths (one conducting only
with a positive amplilicr output and the other conducting
only with a negative amplifier output).

developed across the positive conducting leg is applied

through a IOK resistor to the summing node of the log

amplifier along with the full wave signal through a 20K

resistor from the output of the scaling amplifier. These two

inputs are combined and, due to the non-linear feedback

loop of the log amplifier (consisting of Q14A and QISA)

produce the log of the combined signal at @ This rig-

nal is fed through an identical path (consisting of transistors
Q1SB and Q14B) to the input of the summing amplifier.

The voltage

4.27 The summing amplifier converts the signal to a dc
level. The ripple content of the dc level is attenuated and
the output reduced to provide a dc equivalent of the RMS
value of the ac input signal.

4.28 Attenuator.

4.29 The Attenuator board is a single printed circuit

board and occupies connector 57 on the Main Logic board.
The Attenuator consists of a relay controlled voltage
divider used on dc function that provides selectable scaling

factors of Xl, X.1, and X.01 ; a relay controlled feedback
network used in conjunction with the isolator that provides

selectable gain factors of Xl, X10, and X100; and current
compensation circuitry used in conjunction with the ohms

converter.

4.30 Isolator.

4.31 The Isolator is a single printed circuit board and
occupies connector JB on the Main Logic board. The Isolator
consists of a high open-loop.gain amplifier, a bootstrap
amplifier, and a 3.pole filter.
potentiometrically and operates in conjunction with the

attenuator board as shown in figure 4.10.

4.32 The bootstrap amplifier generates the + and ­supply voltages for the input stages of the isolator, causing
them to track the input signal. This results in an effective
input impedance of greater than 10,000 megohms. The

filter is an active 3-p& Bessel type connected by relay Kl
to a point between the gain stage and the post amplifier of
the isolator. The filter increases normal mode noise
rejection from 10 to 48 dB (at 59 Hz) when Kl is energized.
Filter selection is through the front panel switch or the
remote programming option.

4.33 Switching Bypass.

4.34 The Switching Bypass board is a printed circuit

jumper board and occupies connector IS. The Bypass

board replaces the Switching board when the Ohms and AC
converter options are not used in the DVM. The signals are
routed through the Bypass board in exactly the same manner
as in the Switching board when the dc function is selected.
A block diagram of the Signal Conditioning section with
the Bypass board installed is shown in figure 4.11.

4.35 INTEGRATION.

4.36 The Model 5900 uses an improved version of the
standard dual slope integration method of analogto-digital
conversion, called delayed dual slope. As in the standard
technique, the input signal is integrated for a set time

The amplifier is used

4-9

980453

AC ,NP”T

4-10

Figwe 4.9 - RMS AC Converter

980453

Figure 4.10 Attenuator/lsolntor DC

period to produce a voltage that is directly proportional to
the input signal. At the conclusion of this signal integration
period, the input signal is removed from the integrator and
replaced by a fixed reference voltage whose polarity is
opposite that of the input signal. This causes the integrate
output voltage to discharge at a linear and fixed rate for a
time period that is directly proportional to the voltage
developed during the signal integration period.

This

reference integration time period is measured and displayed

in the instrument readout. The transition from signal to
referenceintegration in the A toDsequence, is accompanied
by switch noise in the form of spikes. Due to this and
normal mode noise which may accompany the input signal,
the standard dual slope technique issubject to noise induced
errors with input signals at or near zero. The delayed dual
slope technique used in the Model 5900 DVM minimizes
this source of measurement error by generating a period of
non-measurement or delay between the two integration

4-11

980453

Figure 4.11 - Signal t&w, Switching flypass

periods. The circuitry used to perform this task include
both the Digitizer and portions of. the Display/Logic section.
In the Digitizer, shown in simplified form in figure 4.12,
this is reflected as an adjustment to the basic shape of the
integrator output signal as shown in figure’ 4.13. The

‘delay’ portion of the integration cycle is initiated imme-

diately following the signal integrate period and is the result

of two factors. First, an’ analog level equal to 180 digits

and of a polarity that resists the axis crossing from occurring,

is produced at the integrator output by a network called
the feed forward circuitry. Second, a capacitor in the feed­back network of the gain stage that follows the integrator
adds to the total delay period. The total effect is a fixed
delay of the axis crossing signal of 200 digits.

4.37 Digitizer.

4.38 The circuitry that performs the A/D conversion is
mounted on the single, printed circuit Digitizer board and
occupies connector J9 on the Main Logic board. The cir­cuitry includes: an integrator and switching network, a
gain stage, null detector, transformer driver, signal and re.
set logic, switch controls and + and - reference supplies.

4.39 INTEGRATOR.

4.40 The Integrator consists of an operational amplifier
with a capacitive feedback path to convert the dc levels
applied to its input to a corresponding ramp voltage at the
integrator output. The use of a dual FET input stage pro.
vides a correspondingly high input impedance and per-

mitting capacitor input coupling during the integration
period and allowing auto-zeroing during reset. The feed
forward circuitry is a voltage divider network that takes a
portion of the reference voltage and applying it to the non­inverting input of the integrator. This results in an equal

amount of voltage appearing at the integrator output.

-.

4.41

The integrator switches consist of junction FET’s,
controlled by circuitry located on the Digitizer. Referring
to figure 4.12, switch Sl conducts during the signal inte­gration period, switch S2 or S3 during reference integration
and S4 and S5 during reset. The output of the integrator is
coupled to the following Gain Stage through two FET’s
connected as current generators. The purpose of these
generators is to prevent loading of the Integrator while
maintaining reasonable coupling to the gain stage input.

4.42 GAIN STAGE.

4.43

The gain stage greatly increases the amplitude of the

integrator output especially in the area near zero to provide

a more clearly defined axis crossing signal for the null
detector to respond to. The gain stage also exhibitslow pass
filter characteristics which, as previously discussed, adds to
the total delay of the integration sequence. This reduces
the total noise response of the system and reduces the wide
band response requirements of the null detector. The cir­cuit consists of a potentiometric amplifier with a pro­grammed gain control, providing gains of 300 for stage inputs

of up to I3 mV and decreasing to 14 for signals above this

level.

4.44 NULL DETECTOR.

4.45

The Null Detector consists of an inverting, open­loop amplifier with an output swing of 5 volts. The Null
Detector

converts

the amplified analog signal (ramp) from

the integrator to a digital level (logic 1 =: +5 volts and logic

=: 0 volts). This digital signal, called either the null

0
detector output or axis signal is used on the Digitizer board
for determining the polarity of the reference to be used for
the reference integration and, by way of the transformer
driver and transformer Tl, the circuitry of the Display/
Logic section of the main assembly.

4-12

-1

980453

Figure 4.12 . Digitizer

4-1.3

980453

PGM E

Figure 4.13 -Integration Timing Dkpm

4.46 TRANSFORMER DRIVER.

4.47 This circuit consists of a complementary emitter­follower, capacitor coupled to the isolation transformer Tl.

4.48 SIGNAL AND RESET LOGIC.

4.49 This circuitry operates from pulse data obtained

through isolation transformers T2, T3 and originating from
control circuitry of the Display/Logic section. The data is

converted into control signals for operating the integration

switches.
4-14

ll

4.50 DIGITIZER LOGIC,

4.5 1

The Digitizer Logic receives its timing information
through isolating data transformers T2 and T3. The logic
converts this information into control signals that operate
the FET switches. The timing of the input data and switch
operation is provided in figure 4.13.

4.52 Ratio, Standard.

4.53

The standard ratio consists of relay KI on the inter-

connect board. When nonenergized, this relay routes the

I

Figure 4.14 - 4.Wire Ratio Option

outputs of the internal zener reference bridge to the
reference amplifier (both located on the reference amplifier
assembly) and produces a fixed + and - IO volts; when
energized (Ratio selected) the relay reroutes the signal flow,
replacing the zener input with the EXT REF input and
converting the +I0 output amplifier to a noninverting gain
of one amplifier.

4.54 Ratio Option.

4.55 The four wire ratio circuitry is mounted on a single
printed circuit board and occupies connector 514 on the
Main Logic board. The 4wire ratio option eliminates ground
loop errors in ratio measurements by permitting the
reference input common lead to float in reference to the
signal input common. The circuitry, shown in figure 4.14,
consists of two gainof-one isolation amplifiers driving a
differential potentiometric amplifier. Field installation of

980453

the ratio board requires removal of jumpers WI and W2 on
the Main Logic board.

4.56 Display Board.

4.57 The Display board is a single printed circuit board
and occupies connectors JI and 52 on the Main Logic
board. The display board is located directly behind and
parallel to the front panel of the instrument; the function
and range control knobs on the front panel are connected
by shafts to the rotary switches on the display board. A
mechanical interlock attached between the two shafts pre­vents the manual selection of incorrect function/range
combinations. The display board contains the function,
the manual and autorange, and the annunciator circuitry.

The circuit is shown in simplified block form in figure 4.15

and described below.

4.58 FUNCTION AND RANGE SWITCHES,

4.59 These generate a negative true output and operate
only in local control (programming not selected). The
function switch has three positions_generating outputs
(from left to right) of AC, DC, and a The range switch
has nine positions and generates the outputs shown in
table 4.2.

4.60 DATA ENCODE

4.61 The output of the range switch is converted to
positive true 1248 BCD logic by this circuitry. The BCD

--

Figure 4.15 . Display Board

980453

Table 4.2 - Range Switch Code

output is the same as produced by the programmer for
remote range selection and is shown in table 4.2. The four
BCD output lines from the data encode are applied to the
up/down counter.

Table 4.3 - Autorange Logic

4.62 UP/DOWN COUNTER.

4.63

The up/down counter is adecade counter capable of
counting up from, 0 to 9 and overflowing to 0, counting
down from 9 to 0 and overflowing to 9, being preset to the
BCD input, and being cleared to zero. In manual range the
up/down counter is held in the preset mode and the output
of the counter always equals the BCD code from the data
encode circuitry. In autorange the BCD input from the

range data encode is inhibited and the output of the counter
is controlled by the autorange logic.

4.64 AUTORANGE LOGIC.

4.65 The autorange logic generates the control pulses,
for advancing

the

counter up or down. Data are received
from the function switch and from the range data decode
circuit, a BCD to IO-line converter. If no range change is
required the circuitry generates no control signals and the
counter is not advanced. An up range signal is generated
during the Program D period if an up range 160% signal is
true and the up range inhibit signal is not false (see

table 4.3). One up range signal is generated per measure­ment cycle. A down range signal is generated during the
Program D period if the down range 15% signal is true and
the down range inhibit signal is not false (see table 4.3).

One down range signal of this type is generated for each

measurement cycle.

In the event that the counter is in a

,forbidden range (not available for thk function selected),

during the clear period, the counter is made to down range

at the clock rate until the counter is in an available range.
The autorange circuitry then operates normally to select

the most appropriate range. The forbidden ranges are

indicated in table 4.3. If the counter output produces an

‘impossible code’ (as could happen when the instrument is
turned on and autorange is selected), the impossible code
logic resets the counter to zero; the autorange circuitry then

selects the appropriate range.

Table 4.4 -Relay Logic Coding

Table 4.5 - Annuncint

980453

4.66 RELAY LOGIC.

4.61 The relay logic is generated by data from the range
data decode and the function switch and is used via optically
coupled isolators on the Main Logic board to control the

attenuator range relays. The codes as shown in table 4.4
indicate the attenuator relay closure.

4.68 ANNUNCIATOR LOGIC.

4.69 The annunciator logic controls the selection of the

annunciator lamps as shown in tables 4.5 and 4.6.

4.70 MAIN LOGICANDCONTROLCI~ClJITRY.

4.71 This circuitry, shown in the block diagram of fig.

ure 4.16, is located on the Main Logic board and consists of
the control and display logic. In general this circuitry

controls all instrument operation including the integration

cycle, ‘times’ the output of the digitizer, and converts this
information into data compatible with the Display board.

4.72 Control Logic.

4.73 This circuitry controls the operation of the instru-

ment and consists of the program logic, program counter,

Table 4.6 - “NO” Annunciator Logic

4-l 7

980453

program clock, read rate generator, master clock, clear
logic, and counter logic. The instrument operates on a five
step program cycle produced by the program circuitry.
This consists of a five stage shift register (or program
counter), a program clock, and control logic. The five out­puts of the program counter correspond to the five program
states (PGM A, PGM B, PGM C, PGM D, and PGM E).
Only one output of the counter is true at any time during

the measurement cycle of the instrument and all of the

4-18

outputs are false when the instrument is in clear. The

program counter is advanced by a gated square wave from
the program clock. The program clock output is driven by
and equal to the master clock frequency divided by IO or
600 kHz and is synchronized with the counter at the start
of each measurement cycle. The correlation between the
master and program clocks causes a IO count lag between
the program counters advancing during the signal integration
period and the counter.

980453

4.74 Program Cycle.

4.75 Preceding the start of the measurement cycle, the

instrument is in a clear state with the counter set to

100000 and the logic in the reset state. Upon receipt of a

read command, whether from the read rate generator or by

an external command, the clear signal is removed and the

counter begins counting. After ten clock counts (100010)
the program counter advances to PGM A. Program A, via
the pulse transformer T3, initiates the signal integrate
period of the integration cycle on the digitizer board. Pro­gram A is terminated after the counter is advanced 100,000
counts. The period is a precise 16-213 millisecond and the

counter now reads 000010 (the counter overflows to zero
at 199,999). At the completion of Program A, Program B
is initiated, lasting for 200 clock cycles.
corresponds to and provides the required digital delay for

the analog delay period between the signal and reference
integrate periods of the digitizer as described in para­graph 4.36. At the completion of the 200 count delay
(PGM B), the l’s, lo’s, and 100’s decades of the counter are
reset, causing the counter to read OBOOOO. At the same time

the program counter is advanced to Program C, which in

turn enables the axis crossing detector. The program counter
remains in this state until (1) an axis crossing signal is
received, indicating the reference integration period of the

digitizer is completed or (2) the counter reaches 160,000,
indicating an overload condition. One of these two inputs

causes the axis flip-flop output to go true, inhibiting the

clock gate and stopping the counter. The program counter

is advanced toProgramD and the A(delta) delay is initiated.
The delta delay lasts for about 1 millisecond and prevents

the ready line from going through until after the program

counter has completed its cycle. Program D lasts for one

program clock cycle and strobes all but the 1OOK latches.
The program counter then advances to Program E which

also lasts for one program clock cycle and strobes the IOOK
latch. At the end of Program E, the Program A-E line goes

false, resetting the read rate oscillator, starting the E (epsilon)
delay which lasts for 5 milliseconds and generates the reset
signal for the digitizer, and generates the clear signal which

sets the counter to 100,000 and resets the logic. At the
end of the delta delay, the ready line goes true generating

the DATA READY output signal and enables the program
logic to receive a new read command. At the completion
of the epsilon delay, the SYSTEM READY signal is
generated and indicates that the instrument is able to
accept an externalread command. This returns the circuitry

to the state at the start of the program cycle.

4.76 Display Logic.

4.77 This circuitry consists of the counter, latches, BCD­to-7 line converters, display strobe, clear logic, decimal
logic, and the counter control logic. The counter consists

This period

of five series connected decade counters and a J-K flip-flop,

and is capable of counting from 000000 to 199999 and then

overflowing to 000000. The counter is driven by the 6 MHz
master clock by way of the clock gate and the counter

logic. The clock gate permits the counter to advance only

during the measurement cycle. The counter logic circuitry
routes the clock signal for normal or superfast operation.
The clear logic operates in conjunction with the clear flip

flop and the counter logic to clear all or portions of the

counter depending on normal or superfast operation for

different parts of the measurement cycle. The latches store

the information from the counters from the last measure­ment cycle in the form of BCD data. The units through

10K latches are strobed (the information at the input of the

latch is transferred to the latch output 1 at Program D; the

1OOK latch is strobed at Program E. The data from the
latches are converted to be compatible with the seven
segment LED displays by the BCD-to-7 line converter. The
converters are also used in conjunction with the decimal
logic to provide leading zero blanking. The LEDs on the
readout board are controlled by the BCD-to-7 line converters
and powered by the driver decoder strobing circuit. This
consists of a one-shot driven by a 120 Hz signal. The strobe
permits the LED’s to operate at their greatest efficiency

while maintaining low overall power consumption.

4.78 Superfast.

4.79 This is a high speed operating mode in which the
instrument is effectively converted to a four decade instru­ment.
considerationsare covered under paragraphs 2.68 and 2.105.
Basically the superfast mode is achieved by bypassing the
least significant decade (l’s) with the counter logic. At the
start of a superfast measurement cycle, the l’s decade is in
the clear mode and the 6 MHz clock is applied directly to
the input of the lo’s decade. The signal integration time of
the digitizer is reduced from 16.2/3 milliseconds to 1.6.2/3
milliseconds. The 200 digit time period nnut remain the
same as in the standard measurement operation so the
instrument is converted back to standard operation during
the 200 count delay. At its completion the operation

reverts back to superfast and the reference integration

period is measured at the same rate the signal integration

period was generated.

4.80 Power Supplies.

4.8 1 There are two separate power supplies used in the
Model 5900; one provides the voltage levels required for
operating the analog portions of the instrument and the
other provides the voltage levels for the digital/display, data
output, and programming. The two supplies use a common
transformer core and primary winding but the supplies
themselves are completely isolated to maintain the common

The actual selection of this mode and timing

4-19

9804S3

Figure 4.17 . Progranr Block Diagram

mode rejection characteristics ofthe instrutient. The

analog

supply provide outputs of +25 volts, +20 volts, and -40
volts, all referenced to analog common (mecca). The digital

supply provides outputs of t5 volts, +5 volts unregulated,
and +I 50 volts, all referenced to digital common.

4-20

4.82 Program.

4.83

The program board is an option provided to allow

external remote operation of the instrument. The circuitry

is mounted on a single printed circuit board. The board is

located above and parallel to the Main Logic board and
mounted to the Main Logic board on standoffs. Electrical

connection between

the

Main Logic board and the Program
board is by way of two cables (13.J3A and J4-J4A). A
portion of one end of the Program board extends through
the rear panel of the instrument, through an opening pro-

vided for that purpose. This portion of the board forms an
edge connector and isdesignated P202 PROGRAM INPUT.

980453

/

4.84

The circuitry, shown simplified in figure 4.17, con­sists of the program logic, data gate, and the command/
timeout circuitry. The program logic converts the control

line data generated at P202 to correspond to the instrument

control lines. The data gate paws or rejects the converted

data; the gate is enabled when the. program switch is
operated and system control is selected on P202. A series
of inputs with their outputs are shown in table 4.7. The
timeout circuitry generates the necessary timeouts for
delayed remote programming. The timeout periods are
covered under paragraph 2.99.

4-21

980453

Table 5.1 -Required Calibration Equipment

Lx

AC

­Qty

(1)

-1

0
0
<I,

0)

0

(1)

~(1)

-5

­(1)

-

Item

aturated Standard Cell Bank
5 cells)

IC Voltage Sources

I:

‘oltage Divider Adjustable

\

0: I Voltage Divider, Fixed

I

00: I Voltage Divider, Fixed

I

qull Detectorl~Voltmeters

P

ihermal Transfer Standard

1

fhermal Voltage Converter

1

9C Voltage Source

1

Pulse Generator*

I

Minimum Use

Specifications

I ppm, certified

D.1 ppm resolution

0.1 ppm linearity
1 PPm,

Output Z 210 Kohms

1 aom.

O;ipu; 2 110 Kohms

I WV sensitivity

35 ppm @ 400 Hz,

50 $rn @ 40 kHz
SO ppm @ IO0 kHz

I ppm resolution
IO voltsvariable, 5On outp”t

-

Suggested

Equipment

-

SPPLEY 106

FLUKE 3328
FLUKE 720A
Fabricated*

-

Fabricated*

FLUKE 845AR

HOLT 6A

HOLT I I
HP745A/746A

-

TEKTRONIX 2101

OTHER

*See Text

1

Resistance Standards

(8)

IOR
I oon
IKS?a
10Ka

100 Ki2

I M&-I
lOMa
100 MZ;2

-

tiomentary Switch, SPST

I

(1)

‘hillips head screwdriver #I

I

Gi-

-

;nsulated Adjustment tool

I

(1)

-

IO Kohm l/4 Watt 5%

(1)

I

zarbon Resistor
I Megohm l/4 Watt 5%

(1)

I

-

larbon Resistor

10

w*
low*
10

pp*

10

w*

Iow*
10

w*

50

w*

80

w*

5%

5%

ESI SRI with corrections
ES1 SRI with corrections
ES1 SRI with corrections
ES1 SRI with corrections

ES1 SRI with corrections
Fabricated*
ES1 SRI with corrections

Fabricated*

-

JFD5284

SECTION 5

CALIBRATION

5.1 SCOPE.

5.2
Model 5900 DMM and the following options:

5.3 GENERAL.

5.4
and is precisely calibrated under closely controlled condi­tions, prior to leaving the plant. The procedure provided in
this section isdesigned to recalibrate the Model 5900 and to

keep the instrument operating within specifications for
indefinite periods of time. If the instrument is equipped
with the rear panel selectable input option, set the FRONT/
REAR switch to the appropriate position for each of the
checks in this section calling for the application of input
signals to the instrument.

This section describes the calibration of thcKeithley

Model 52 Ohnx/DC Converter

Model 32 AC/DC Converter, RMS

Model 33 AC/DC Converter. Averaging

Model 62 4-Wire Ratio

The Keithley Model 5900 undergoes rigorous testing

Table 5.2. Fixed Voltage Dividers

Range outpu1

Ratio Used on lmpcdancc

The absolute accuracy of each

age applied (i.e., the voltage

‘oo”~pdd”,y / /;~cJntmustalsobe 1

Suitable lypes of resistors for the IWO ranges are listed
below.

I Megohm

100 Mcgohm 25 ppm TC metal film of known value

5.10 DC Voltage Sources.
To produce voltage levels of necessary accuracy,

5.11
special techniques are required.
generating these voltages are shown in figures 5.1 and 5.2.

5.12 IOVOLT SOURCE

2 ppm TC wirewound of known value

Suitable methods of

5.5 Required Equipment.

5.6
provided in table 5.1. The specific types of equipment in
the Suggested Equipment column are acceptable for cali­bration and provided as a guide in selecting suitable equip­ment; instruments having operating characteristics equal to
or better than those indicated may be substituted.

5.7 Fabricated Calibration Equipment.

5.8
quired for dc range calibration. The dividers provide the
required accuracy and low output impedance not normally

available on commercial equipment. The specifications of

the dividers are indicated in table 5.2.

5.9 Two standard resistors are called out for ohms
calibration, for which no commercially available standard
resistors having the required accuracy are presently avail­able. These can be fabricated by mounting precision
resistors in a standard minibox on 5.way binding posts.

A list of the equipment required for calibration is

Two fixed voltage dividers, 10: 1 and 100: 1, are re-

5.13

not only for calibrating the IO volt range. but also as a

reference for generating highly accurate 1, I, 100, and 1000

volt levels. The 10 volt source used must satisfy the

following requirements.

A source filling these requirements is shown in figure 5.1.
This circuit consists of a null detector, II-decade voltage
divider, a dc voltage supply, and a bank of saturated
standard cells. Two advantages of this particular hookup
are that; (a) there is minimal loading of the standard cells
and (b) stability, not accuracy, is the primary requirement

of the dc voltage supply.

5.14

by setting the voltage divider to the value of the standard
cells. The dc voltage source is then adjusted to produce a
null on the null detector. The accuracy of the IO volt
source is within I. I ppm.

Aprecise and traceable source of IOvoltsis required,

a. It must be traceable to the National Bureau of

Standards;

It must have a total accuracy of 1 .I ppm;

b.

It must have a low output impedance

c.

The output of this circuit is set to a precise 10 volts

S-1

980453

5-2

Figure 5.2 - Generating Accurate DC Levels

Range

10 Volt

Source

Table 5.3 - DC Source Accuracies

Fixed Total

Divider

Accuracy

24 hr.
DMM

Accuracy

Times

Better

10
I

.I

100
1000

I.1 ppm

1.1 ppm

1.1

ppm

1.1 ppm

1.1 ppm

- I.1 ppm
1 pm 2.1 ppm
1

PPm

1 PPm 2.12 ppm
1 PPm 2.12 ppm

5.15 OTHER SOURCES.

5.16 The remainder of the dc sources can be generated by
the circuits shown in figure 5.2. Each of these hookups use

a calibrated 10 volt source having the characteristics of the
one previously described:

5.17 ACCURACY. DC.

5.18 The accuracy of the dc voltage sources is obtained’

by adding the various sources of error in each hookup;

10ppm 9
10ppm 4.8

2.1

ppm

20

pm

4.8

lOPPm 4.7

1OPPm 4.7

errors in this discussion are defined in parts per million
(ppm). For the 10 volt source, the error is the sum of the
standard cell bank (certified at 1 ppm) and the voltage
divider (0.1 ppm), giving a constant 1.1 ppm. In table 5.3
is shown the errors ofeach voltage source, the totalaccuracy
of each hookup, the accuracy of the Model 5900 DMM, and
the degree to which the sources exceed the required
accuracy of the DMM (4 to 10 times better is the suggested
accuracy ratio per MIL-M-38793).

DC. With DMM used to monitor DC output, dc source is
adjusted to desired voltage. Transfer standard is then used
per manufacturer instructions.

ACSOURCE

,

o­o-

TRANSFER STANDARD

AC. The ac source is adjusted to produce a null on transfer
standard. The ac source output is now calibrated and can
be used as a precision source for the recalibration of the
5900 AC Converter.
NOTE: Because of the low input impedance of the transfer

standard, the DMM input leads must be connected as close
to the transfer standard input terminals as possible.

rrgure J.3 n c 3ource

s-3

980453

Table 5.4 _ AC Source Accuracies

~

1000 Volts

400 Hz

52

wm

5.19 AC Voltage Sources.

5.20 The generation of accurate ac signals for calibrating

the ac converter ranges, requires the use of a thermal

transfer standard and a precise dc standard as well as a stable
ac source. Sufficient accuracy can be obtained by using a
dc source and the Model 5900 being calibrated (immediately
after the dc calibration has been completed). The circuitry
connections are shown in figure 5.3. Information on the use

of the transfer standard can be obtained from the operators
manual accompanying the standard. The 5900 is used to
set the dc source to the desired voltage; the thermal transfer
standard is then used to calibrate the output of the ac
source. The calibrated ac source is used to calibrate the
5900 ac converter. This procedure is repeated for each
range.

5.2’ ACCURACY, AC.

5.22 The accuracy of the ac source is equal to the sum of

the transfer standard accuracy and the accuracy of the dc
source. The accuracy of the setup for each range and fre­quency used in the calibration procedures as well as the
specified accuracy of the converters is provided in table 5.4.

42

200ppm

wm

1

600 ppm

miscellaneous hookup cables required for the calibration
procedure are readily available. Verify that all of the equip­ment used in the calibration is warmed up for the period
prescribed by the manufacturer to reach full accuracy.

5.28 Calibration Points.

5.29 The location of the calibration points (except ac)
used in the calibration procedure are shown in figure 5.4.
The ac calibration points are shown in figure 5.8. Access to

the calibration points is gained by removal of the top
cover; the cover is secured to the DMM by captive screws
located in each of the four corners of the cover. Directly
beneath the cover is located a metal shield with access holes
to calibration points (except ac). The shield is part of the
instrument internal guard system and helps to reduce noise.

For reference, an abbreviated form of the basic calibration

procedure is silkscreened to the top of the shield. The

shield is to be left in place unless specific instructions are

given for removal.

5.30 Environmental Considerations.

5.31

The ambient temperature of the calibration environ-

ment shall be held to 23OC + l°C.

5.23 PRELIMINARY PROCEDURE.

5.24 Warmup.

5.25 Apply power to the instrument and allow two (2)
hours of warmup time before calibrating with instrument
covers in place.

5.26 Familiarization.

5.27 Prior to starting the procedure, read all of the steps
and verify that all of the necessary equipment, tools, and

5-4

NOTE

In instruments equipped with the optional 4.wire
ratio option it is necessary to remove the 4.wire ratio
circuit board and connect jumpers W2 and W3 on the
interconnection board. The shield is removed for

~CCCSS to the circuit board and then replaced prior to

calibration of the instrument.

5.32 RECALIBRATION PROCEDURE.

5.33

The procedure is designed to produce the highest
accuracy in the least number of steps while minimizing
interaction between adjustments. To ensure accuracy, do

980453

Figure 5.4 -Adjustment Locations

J-5

980453

not deviate from the order of adjustments as given in the
procedure.

Removal of covers exposes potentially lethal voltages.

5.34 Isolator Zero.
a.

Select DC function and .l volt range. Short the +
input terminals; connect microvoltmeter
ANALOG OUTPUT terminals. Set DC OFFSET
(front panel) to the center of its mechanical spa”.

b. Adjust RI4 (.lV Zero) on Isolator for a micro-

voltmeter reading of less than 100 microvolts.

c.

Replace the jumper across the t INPUT terminals
with a 1 Megohm resistor. Adjust R3 (1OOV ZERO)
for a reading of less than I millivolt.

d. Replace the resistor with a jumper. Select IOV

range. Adjust R7 (IOV Zero) for a reading on the
microvoltmeter of less than 20 microvolts.

to

c. Repeat the above steps as required until all steps

are calibrated.

d. Verify that the voltage at the ANALOG OUTPUT

terminals (on rear panel) is the same as the voltage
on the input terminalsat various input levels (+lOV,
klV, etc.).

5.36 DC RANGE CALIBRATION.

5.37

DC function and range as listed for each step. Adjust the

indicated control for a readout equal to the input voltage.

Apply inputs listed in the following table. Select

e.

Repeat the above steps until all ranges are zeroed
within the indicated tolerance.

5.35 DC Voltage Zero and Gain.
a.

Select DC function and IOV range. Apply a” input
of +OO.OOlOV. Observe readout and reverse polarity
of input (-OO.OOlOV). Adjust R27 (+lO DIGIT
BAL) for same readout for 9” or “-” inputs. Ad-

just R40 (+lO DIGIT SPAN) for + 10 digits.

b.

Apply inputs listed in following tables to the front
panel input terminals and the rear panel ratio input
terminals. Select mode as listed for each step and
adjust indicated control for a readout of +lO.OOOO.

Ratio Select

F/P Input

r--

Input Mode (on Digitizer)
t1.000OOV Ratio RS (-RATIO LIN)
+l.OOOOOV Ratio R64 (+RATIO LIN)
t10.000OV Ratio R2(-IOV RATIO)

DC
DC

Adjust

R4(-IOV)
R57 (+lOV)

5.38 OHMS CALIBRATION (Figure 5.4).

5.39 Ohms Zero.
a.

Select 0MS2 function and the IO Megohm range.

Short the + INPUT and + CURRENT terminals

together. Adjust R56 (0 ZERO) for zero readout.

b. Remove short from INPUT and CURRENT ter-

minals. Connect a IO Megohm standard resistor

across the + INPUT terminals. Do not connect the
+ CURRENT lead (figure 5.5).

+ INPUT

70 MEGOHMS

- lNP”T

-I

4:1

5-6

Figure 5.5. Ohms Input Connection

5.40 OHMS RANGE.

YXO453

5.41 AC CALIBRATION (Model 33).

5.42 AC Converter Zero (Figure 5.8).

Figure 5.6 . Connectiunsfor Ohms Range Adiustment

I

Connect input with 4.wire configuration (figure 5.7)

b.

I

I I

and complete the adjustments of the low ranges.

a. Remove Scaling Amp, insert Scaling Amp Bypass

card (Keithley P/N 5900-410617) in its place, and
install AC Converter 011 extender. Select AC
function, any range, and leave illput open,

b. Connect the microvoltmeter with a IO kilohm

resistor in series with the positive lead to TP3, with
negative side to TP6 (common). Adjust R35 for a
microvoltmeter reading of less tba” IO cNolts.

c. Cormect the + microvoltmeter lead alternately

between TPS a”d TPI. Adjust R5 so that the
voltages at TPS add TPI are equal (balanced) within
approximately +IO~olts(oppositepolarities). The
voltage at each of the two test points must be less

than +20 /NoIts.

5.43 Frequency Response.
a. Depress FILTER switch. Apply I volt at 400 Hz

and record readout. Apply 1 volt at 100 kHz and
adjust Cl3 for same readout (+I0 digits) as ob-

tained with 400 Hz.

Figure 5.7 - 4. Wire Connections

b. Remove extender fro”1 AC Converter; remove

Scaling Amp Bypass cud. Install AC Co”verter and

Scaling Amp into instrument.

c. Apply the inputs listed in the followiop t;lhlr a”d

adjust the indicated co”trol 01, Scaling Amp for a
readout equal to the illput.

s-7

980453

5-8

I -!

Figure 5.8 - ACAdjustment Locations

t I

980453

Ein

.01000

1 .ooooo

10.0000

100.000

1 1000.00 1 400 Hz (

-

I

1 500.00 1 40 kHz 1 CZO(INFW H.F.)

5.44 RMS AC CALIBRATION (Model 32).

Freq.
400 Hz
400 Hz

400 Hz

400 Hz

-

AC OFFSET (front

RI I (1V L.F.)

R8 (1OV L.F.)
R7 (IOOV L.F.)
R3 (IOOOV L.F.)

Cl (1OOOV H.F.)

set to center of span

Adjust

panel)

e. Connect + microvoltmeter lead to TP3. Adjust R31

for 0 + 30 mV. Remove t microvoltmeter lead
from TP3.

f. Connect + microvoltmeter l&to TP4. Adjilst R41

counterclockwise until the voltage at TP4 reads
0 ?1 5 /.tV. Remove microvoltmeter leads a”d re-

move jumper across DVM input.
g. Apply -1 SIOOOOV DC and “otc DVM display.
h. Reverse polarity of input to +i.OOOOOV DC and

adjust R28 to obtain approximately the same DVM

display as obtained in step g. Repeat steps g and h

until the two readings are within .OI% of each

I

other.

Apply tO.10000 to DVM input and note DVM

i.

display.

Reverse polarity of input to -0.10000 and verify

j.

DVhI display is within +5 digits of the reading

obtained in step i. If not, use R31 to balance the

readings.

Remove DC supply from DVM input.

Use 10 KS2 resistor in series with + lead of micro.

voltmeter.

Set DVM power switch to off. Extract converter.
Set Sl and S2 to DC (away from center of board),
replace converter and set power switch to on. Se­lect AC and 1 volt range on DVM front panel.
Allow 10 minutes for temperature to stabilize.

Connect jumper across DVM input terminals. Con-

nect the microvoltmeter to TPI (t) and TP5 (-).

Adjust RI7 for a microvoltmeter reading of 0 +

30 /.tVuv. Remove t microvoltmeter lead from TPI.

Turn R41 fully clockwise.
Connect microvoltmeter + lead to TP4. Adjust R42

for a microvoltpxaer reading of +20 pV + 10 pV.
Connect t microvoltmeter lead to TP2. Adjust R33

for a microvoltmeter reading of 0 + 30 PV. Re-

move microvoltmeter t lead from TP2.

NOTE

R54 is a” FSV adjustment and is reset only if major
repairs have been perfornud on the converter. In this
event, perform the following adjustment:

Apply a calibrated l.OOOOOV RMS pulse train with a
crest factor of 7 and a period of 1 millisecond (1 kHz
repetition rate). Adjust RS4 for a readout of I .OOOOO.
Remove the pulse generator from the DVM input and
continue with the calibration procedure starting at
step k.

k. Set power switch on DVM to off, extract converter,

set Sl and S2 to AC (toward center of board). Re­place converter in DVM. Reapply power and allow

10 minutes for temperature to stabilize. Select
FILTER.

1. Connect the AC source to the DVM input terminals.
Apply the inputs listed in the following table and
adjust the indicated control for the proper readout.

s-9

980453

I l-i??-+ I I

Range
1v 1 .oooo 500 Hz

1v

Repeat steps for R58 and ax. offset until no

Voltage Freq

.I000 SO0 Hz a.c.offset 0.10000

adjustment is required.

Adjust Readout

R58 1 .ooooo

f. Remove jumper from high side of reference input

to comma”. Connect the jumper between low
reference input and common. Adjust R9 for a
readout of -10.0000. Remove jumper and verify
that the readout does not change by more than one
digit.

g. Apply +l.OV to both signal and reference inputs.

Verify a readout of t10.0000.

IOOOV 1 1000.0 t 500 Hz

I ooov

IV 1 1.0000 ( 50 kHz

IOV 1 10.000 1 500 Hz

IOV

I oov
IOOV

*Use an insulated screwdriver when adjusting the

capacitors. High voltage present on Cl I.

I

5.45 4WIRE RATIO CALIBRATION.

DC calibration of the instrument must be completed
before calibrating 4wire ratio. The DC calibration

must be performed with the 4.Wire Ratio boaid re­moved andjumpers installed across W2 and W3 on the
interconnection board.

a. Install 4.Wire Ratio board; remove jumpers across

b. Connect -1.OV to front panel INPUT terminals;

500.00 1 40 kHz’ ! Cl 1’ ! 500.000 1

I ~~~ ,

10.000

100.00 500Hz R5 100.000
I00.00

W2 and W3. Select RATIO, IOV RANGE, and DC
function.

connect +l.OV to REF INPUT terminals on rear
panel. Connect a jumper from high side of reference
input to ANALOG COMMON (on rear panel).

50kHz C7’

SOkHz C4* I00.000

NOTE

1 R3 I 1000.00

1 C9* 1 1.00000
1 R7 I 10.0000

10.0000

0 ““N!

R10 R12 AB

I

-xi-J-

Figure 5.9.4.Wire Ratio Adjustment Locations

5.46 TROUBLESHOOTING

5.47 This procedure is provided to aid in locating the
cause of an instrument malfunction. The procedure consists
of a systematic basic instrument operation check, a table
of symptoms and probable causes, and a brief description
of major areas of the instrument circuitry from a trouble­shooting standpoint. To eliminate as much as possible

redundant material, frequent reference is made to informa.
tion located in other sections of the manual.

6.46 Troubleshooting Equipment

5.49 The equipment listed in table 5.1 can be used for
the procedure with the addition of an oscilloscope such as
the Tektronix type 453. Access to the main circuitry is
gained by removal of the top cover and shield.

-I

c. Adjust R12 on 4.Wire Ratio board for a readout

of -10.0000 (figure 5.9).

d. Increase voltage at INPUT terminals to -10.0 volts;

increase REF INPUT to t10.0 volts. Adjust RlO for
a readout of -10.0000.

e. Repeat steps b through c until both are achieved

without further adjustment.

5.60 Power Supply Check

Removal of covers exposes potentially lethal voltages.

Avoid contact with internal electrical connections

5.51
cuitry, check that all the supply voltages are present. If a
discrepancy is found, proceed to table 5.5.

Before proceeding with the analog and digital cir.

Table 5.5 -Power Supply Check

Low or Zero output of Supply:

Set power switch to OFF.

1.
Remove all plug in boards to eliminate possible

2.
source of shorts.

Apply power and recheck supply output.

3.

a. If normal, check plug in boards
b. If low, check components on main board

for excessive heat dissipation.

No output of any Supply:

Disconnect power cable from line voltage and

1.
back of instrument.

With power switch on, check for continuity

2.
(Low DC resistance) between HI (pin 2) and

Lo (pin 1) of 3203 (typically, 110 volt range is

12a 220 volt range is 3%X). An open indicates

a failure of F201, S201, S202, or Tl.

5.52 Operational Check

5.53
the basic instrument functions in a prescribed sequence and

5.54 Preliminary Instrument Setup

The check consists of narrowing down the problem

to a specific area or circuit. This is done by checking out
referring to the troubleshooting guide when the instrument

fails to perform as indicated.

a. Select DC function, I Range, Filter OUT, Ratio

Out, Data Output Out, Remote Control Out, and
Rate Control fully clockwise.

Verify the line voltage selector on the DMM rear

b.

panel is positioned for the available line voltage
and connect power cable.

Perform the checks indicated in Table 5.6 if the

c.

instrument fails to provide the indicated output,

refer to table 5.7 for assistance.

Table 5.6 - ODerational Check

across + and -

volt (DC sburce)

6.

Select 10 volt on
DMM

7.

Select 100 volt
on DMM

8. Select 1000 volt
on DMM

9. Increase input voltage

to -200

Reduce DC Source and remove source from

input

I

5.57 MEASUREMENT LOGIC. These circuitsare covered
in paragraphs 5.58 through 5.63 and include the control
and display logic. Symptoms of a failure in this area is the
Display does not change with a change of input signal
(see block diagram in figure 4.16 and schematic -figure 6.3)

5.58 CLOCK OSCILLATOR. The clock oscillator runs
continuously at 6 MHz. If there is no signal, repair the clock.

(5. MHz for SO Hz operation). Ql, lJ38C, YI, U13A

*May require adjustment of front panel offset

range

range

range

volts

- 00.1000

- 000.100

- 0000.10

-

0200.00

I

5.55 Circuit ljascriptions

5.56 The remaining paragraphs describe the operation
of the instrument circuitry from the standpoint of specific
operating characteristics. These are to be used in trouble­shooting to verify proper operation. The majority of the
circuitry operates in a linear flow; that is, a signal is genera­ted at one point and processed, encoded, decoded, or con­verted through various other circuits. If the output of one
of the circuits is incorrect. the circuit is bad.

5.59 DECADECOUNTERS. These IC’s(Ul4.UlS,U33A)
are the decade counters and are driven by the 6 MHz clock
and run only during measurement cycle. If they do not run,
replace them.

5.60 LATCHES. These 1C’s (U7.Ul I, U38B) store the
information appearing at the input line (2, 6, 7, 3) upon

receipt of a transfer pulse (PGMD) the stored date

5-l I

Table 5.7 . Troubleshooting Guide

Symptom

Display Blank

Left 3 digits blank
Decimal point wrong position

Display does not change with

a change in input signal

Diagnosis

Range Logic
Instrument locked up

Probable Cause

Power Supply

leading Zero Blanking
Annunciator Logic
Clock
Decade Counters
Measurement Logic

Reference

Pam. 5.50

Para. 5.61
Pam. 5.66
Para. 5.58
Pam 5.59
Para. 5.57

Will not read full scale

appears and remains at output lines (16, 10, 9, 15) until
the next transfer pulse. (PGMD).

5.61

BCD TO ‘I-LINE CONVERTERS. These units Ul
through U6 convert the data from the counters to ‘I-line
for the display and provide the leading zero blanking
function. These units may be checked by swapping if a
malfunction is suspected.

5.62 READ-OUT. The LED’s on the readout board
(LED 1 through LED 6) are controlled by the BCD to

7.line converters and are powered by the driver decades
strobing circuit (U44, Ql9). Failure of strobe circuit is
indicated by blank display or excessive current drain

from +SV regulated supply.

5.63 CONTROL LOGIC. This circuit controls the opera­tion of the instrument and consists of the program logic
(U38B, U38D, Ul3D, U32A, U38A, U36A.E), program

’ Integrating Capacitor C8
Digitizer Logic
Isolator

Table 5.8
Table 5.9

counter (U37), read rate generator (Q43, Q42, Q9, QlO,
U31B. U30A), program clock (U39), clear logic (U28A, I$,

U29B), counter clear logic (Ul9A, Ul3F, U27B, U27A,
U34C, U20A, C, D, Ul3E, U34D), decimal logic (U41),
auto range logic (U4OA, D, U26A, U19B, D), are axis
crossing/polarity logic (Q2, Q3, U32C, U3OB, U26B,
U29A). Failure of any of above circuits would be indicated

by a locked-up display. See figure 4. I3 for timing and wave.
form diagram.

5.64 DIGITIZER LOGIC AND IOV REFERENCE AMP­LIFIER. (See block diagram, figure 4.12 and schematic

figure 6.13). This circuitry performs the A/D conversion.
It is mounted on a single PC Board and mates with

connector J9 on main logic board. The circuitry includes:

integrator and switching network, gain stage, null detector,
transformer driver, signal and reset logic, switch controls
and 310 volt reference supplies (see paragraph 4.38
through 4.5 I for theory of operation). For troubleshooting
chart on digitizer and 100 reference amplifier see table 5.8.

5-12

980453

5-13

980453

Table 5.9 - Troubleshooting Chart -

Isolator and Attenuator Boards

Table 5.10 - Troubleshooting Chart -Optional Accessories

Sympton

1, Unstable, Noisy Reading a. Oscillation of AR2,

on all functions

2. Won’t Read Full Scale

3. Display locked on over- a. Ql
load

4. Excessive Input Bias

Current

Probable Cause

or AR4

b. BadQ6

c. Filter circuit AR5

Kl (Isolator)

d. Attenuator relays

Kl,K2,K3,K4

a. Q8 or Q9
b. See table 5.8

b. AR3 (Check AR4

pin 6 if 20 volts
replace AR3)

c. Q6
d. Q2, Q3, Q4, or QS

e. See table 5.8
a. Adjust R3, R7

b. Ql failure if cannot

adjust

REPLACE “l,C

5.65 ISOLATOR. The isolator is a single printed circuit
board and mates with connector 18 on the main logic
board, The isolator operates in conjunction with the
attenuator board as shown in figure 4.10. See table 5.9 for
troubleshooting information.

5.66 ANNUNCIATOR LOGIC. This logic controls the
selection of annunciator, autoranging and polarity as shown
in tables 4.5 and 4.6, and schematic figure 6.17. Failure
of these circuits would cause improper range coding,
improper annunciation, improper decimal placement, or
improper autoranging.

5.67 OPTIONAL ACCESSORIES. Options include AC
converter, RMS AC converter, ohms converter, remote
programming, and four-wire ratio. See troubleshooting
guide table 5.10 for more information.

5.68 BOARD REVISION.

5.69 Every effort is made to keep the manual con-

current with the instrument despite changes to the design,

which are an inevitable adjunct of the manufacturing pro-

cess. The manual is updated and periodically reprinted
throughout the year. In between printings, Addendums
and Errata Sheets are added to the manual if required to

implement the reprinted copy.

5.70 Any design change is accompanied by a” updating
of a board revision. Such change could be as simple as a
revised hole size or as complex as major modifications of
the circuitry. The revision of a board is indicated by the
letter preceding the assembly number stamped on the
board; the revision of the assembly drawing in Section 6 or
on a” Errata Sheet is indicated by the letter following the
assembly number, located below the drawing. Comparing
the revision letters can indicate how closely the drawing

corresponds to the hoard.

5-14

980453

r

Table 5.10 -Troubleshooting Chart-Optional Accessories (continued)

Table 6.1- Sii htammxtion List

980453

6-2

.I

Y

6

I

21 1

sf I^

-

C4

t

>

--.

-I-------

I

P

2

­3j

-

----__----_------

-,

980453

r

I
I
I

I
I
I
I
I

I
I

I
I

I

I
I
I

I
I
I
I
I
I

I
I

I

Figure 6.7 -Layout, Switching (403625)
6-10

rC(

“,’

16”

G”IRO--~---------------+

T T I

, , , 0 *w

T

Figure 6.8 Schematic, Switching

6-1 I

980453

Figure 6.9. Layout, Isolator (403624/

6.12

E

Y n

980453

Figure 6.11 -Layout, IOVReference Amplifier (403916)

6-14

Figure 6.12 -Layout, Digitizer (403626)

-..--L- I

0

J