Keithley 3940 User manual

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Publication Date: March 1991
Document Number: 3940-900-01 Rev. .A

WARRANTY
Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a
period of 1year from date of shipment.
Keithley Instruments, Inc. warrants the following items for 90days from the date ofshipment: probes, cables,
rechargeable batteries, diskettes, and documentation.
During the warranty period, we will, at our option, either repair or replace any product that proves to bede-
fective.
To exercisethis warranty, write or call your local Keithley representative, or contact Keithley headquarters in
Cleveland, Ohio. You will begiven prompt assistanceand return instructions. Sendthe product, transporta-
tion prepaid, to the indicated service facility. Repairs will be made and the product returned, transportation
prepaid. Repaired or replaced products are warranted for the balance of the original warranty period, or at
least 90days.
LIMITATION OF WARRANTY
This warranty doesnot apply to defectsresulting from product modification without Keithley’s expresswrit-
ten consent, or misuse of any product or part. This warranty also does not apply to fuses, software, non-re-
chargeable batteries, damage from battery leakage,or problems arising from normal wear or failure to follow
instructions.
THIS WARRANTY ISIN LIEU OF ALL OTHER WARRANTIES, EXPRESSEDOR IMPLIED, INCLUDING
ANY IMPLIED WARRANTY OF MERCHANT ABILITY OR FITNESS FOR A PARTICULAR USE. THE
REMEDIES PROVIDED HEREIN ARE BUYERS SOLEAND EXCLUSIVE REMEDIES.
NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR
ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT
OF THE USEOF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS
BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAM-
AGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTSOF REMOVAL AND INSTALLATION,
LOSSESSUSTAINED AS THE RESULT OF INJURY TO ANY PERSON,OR DAMAGE TO PROPERTY.
INSTRUMENTS
Instruments Division, Keithley Instruments, Inc.
l 28775 Aurora Road l Cleveland, Ohio 44139 * [phone] l Fax: [phone]
WEST GERMANY: Keithky Instruments CmbH l Heiglhofstr. 5 l Munchen 70 l 089-71002-O l Telex: 52-12X% l Fax: [phone]
GREAT BRITAIN: Koitbley Instruments, Ltd.
l The Minster l St?,Portman Road l Reading, Berkshire RG 3 IEA l 01144 734 575 666 l Fax: [phone]
FRANCE Keitbky Instruments SARL
l 3 Allee des Garays . B.P. 60.91124 Palaiseau/Z.I. l I-6-0115 155. Telex: 600 933 l Fax: [phone]
NIXHERLANDS: Keithley Instruments BV
l Avelingen West 49 l 4202 MS C&in&an l P.O. Box 559 l 4200 AN Gortnchem .0X+0-35333. Telex: 24 684 l Fax: [phone]
SWITZERLAND: Keithley Instruments SA 0 Kriesbachstr. 4
l t%W Dubendorf l 01-821-9444 l Telex 828 472 l Fax: [phone]
AUSTRIA: Keitbley Instruments GesmbH
l Rosenhugelstrasse 12 l A-1120 Vienna l (0222) 84 65 48 e Telex: 131677 l Fax: [phone]
ITALY: Keitbley Instruments SRL
l Vi&S. Gbnignano 4/A -20146 Mtlano .02-4120360 or M-4156540 l Fax [phone]

Operator’s Manual
Model 3940
Multifunction Synthesizer
01991, Keithley Instruments, Inc.
All Rights Reserved
Instruments Division
Cleveland, Ohio, U. S. A.
Document Number: 3940-900-01

All Keithley product names are trademarks or registered trademarks of Keithley Instruments, Inc.
Other brand and product names are trademarks or registered trademarks of their respective holders.

Safety Precautions
The following safety precautions should be observed before using the Model 3940Multifunction Synthesizer and any
associated instruments.
This instrument is intended for useby qualified personnel who recognize shock hazards and arefamiliar with the safety
precautions required to avoid possible injury. Read over this manual carefully before using the instrument.
Exercise extreme caution when ashock hazard is present at the test circuit. The American National Standards Institute
(ANSI) states that a shock hazard exists when voltage levels greater than 30V rms or 42.4V peak are present. A good
safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring.
Inspect the connecting cablesand test leads for possible wear, cracks, or breaks before eachuse.
For maximum safety, do not touch the test cablesor any instruments while power is applied to the circuit under test.
Turn off the power and discharge any capacitors before connecting or disconnecting cablesfrom the instrument.
Do not touch any object which could provide a current path to the common side of the circuit under test or power line
(earth) ground. Always make measurements with dry hands while standing on adry, insulated surface capable of with-
standing the voltage being measured.
Instrumentation and accessoriesshould not be connected to humans.

Table of Contents
SECTION 1 - General Information
1.1 INTRODUCTION .............................................................. l-l
1.2 FEATURES ................................................................... l-l
1.3 WARRANTYINFORMATION .................................................... l-2
1.4 MANUALADDENDA .......................................................... l-2
1.5 SAFETY TERMS AND SYMBOLS .................................................. l-2
1.6 UNPACKING AND REPACKING ................................................. l-2
1.6.1 Unpacking ................................................................. l-2
1.6.2 Shipment Contents ........................................................... l-2
1.6.3 Operator’sManual ........................................................... l-2
1.6.4 Repacking For Shipment ....................................................... l-2
1.7 OPTIONAL ACCESSORIES ...................................................... l-3
1.8 SPECIFICATIONS ............................................................. l-3
SECTION 2 - Getting Started
2.1 INTRODUCTION .............................................................. 2-l
2.2 INSTALLATION .............................................................. 2-1
2.2.1 InstallationLocation.. ........................................................ 2-l
2.2.2 Fan.. ..................................................................... 2-l
2.3 LINE VOLTAGE SUPPLY ........................................................ 2-2
2.3.1 Line Voltage Selector Switch .................................................... 2-2
2.3.2 Line Receptacle Connection ..................................................... 2-2
2.3.3 LineFuse .................................................................. 2-2
2.4 KANDLINGPRECAUTIONS ..................................................... 2-3
2.5 BASICOPERATION ............................................................. 2-3
2.5.1
FrontPanelSummary ......................................................... 2-3
2.5.2 Typical Test Connections ...................................................... 2-3
2.5.3 Operating Examples .......................................................... 2-5
SECTION 3 - Operation
3.1 INTRODUCTION .............................................................. 3-l
3.2 FRONT PANEL AND REAR PANEL DESCRIPTION ................................... 3-l
3.2.1 Front Panel Description ........................................................ 3-l
3.2.2 RearPanelDescription ........................................................ 3-12
3.3 Input and Output Connections .................................................... 3-14
3.3.1 InputConnections ........................................................... 3-14
3.3.2 OutputConnections .......................................................... 3-15
3.4 STARTUP .................................................................... 3-16
3.5 OPERATING PROCEDURES ..................................................... 3-17
3.5.1 Setting Parameters Using Numeric Keys ........................................... 3-17

3.5.2
3.5.3
3.5.4
3.5.5
3.5.6
3.5.7
3.5.8
3.5.9’
3.5.10
3.5.11
3.5.12
3.5.13
3.5.14
Setting Parameters with MODIFY ................................................ 3-18
ErrorCodes ................................................................ 3-18
UnitsConversion ............................................................ 3-22
Frequency Programming ....................................................... 3-22
Amplitude Programming ...................................................... 3-23
DC Offset Programming ....................................................... 3-23
AC Amplitude and DC Offset Relational Restrictions ................................. 3-24
Waveform Selection, Square-Wave Duty Factor, and Synchronous Output .................. 3-26
Oscillation Mode and Trigger Source Selection ...................................... 3-28
Mark, Space,and PhaseParameter Programming .................................... 3-29
StopLeveland~S~C ........................................................ 3-32
SynchronousOperation ....................................................... 3-34
Frequency Sweep Operation .................................................... 3-34
SECTION 4 - GPIB Interface
4.1
4.1.1
4.1.2
4.1.3
4.1.4
4.1.5
4.1.6
4.1.7
4.1.8
4.1.9
4.2
4.2.1
4.2.2
4.3
4.3.1
4.3.2
4.4
4.5
4.6
INTRODUCTION .............................................................. 4-l
GPIBOverview .............................................................. 4-l
Major GPIB Specifications ...................................................... 4-l
Bus Line Signals and Operation .................................................. 4-2
GPIBHandshaking ........................................................... 4-2
Data Transfer Example ........................................................ 4-3
BasicTalkerFunctions ......................................................... 4-3
BasicListener Functions ....................................................... 4-4
BasicControllerFunctions ...................................................... 4-4
Multi-Line Interface Messages ................................................... 4-4
OVERVIEW OF MODEL 3940GPIB INTERFACE ...................................... 4-6
Introduction ................................................................ 4-6
Specifications ............................................................... 4-6
MODEL 3940PROGRAM CODES .................................................. 4-13
Model 3940Parameter-Setting Messages ........................................... 4-13
Model 3940Inquiry Messages ................................................... 4-26
TYPICAL EXECUTION TIMES .................................................... 4-35
PROGRAM CODE SUMMARY TABLE .............................................. 4-40
SAMPLEPROGRAMS .......................................................... 4-45

List of Illustrations
SECTION 2 - Getting Started
Figure 2-l FrontPanelSummary...................................................... 2-4
Figure 2-2 Typical Test Connections . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
SECTION 3 - Operation
Figure 3-l FrontPanel .............................................................. 3-2
Figure 3-2 RearPanel .............................................................. 3-12
Figure 3-3 Logic Input Circuits ....................................................... 3-14
Figure 3-4 Analog Input Circuit ....................................................... 3-14
Figure 3-5 Main Synthesizer Sync Output ............................................... 3-15
Figure 3-6 Sub Synthesizer Sync Output ................................................ 3-15
Figure 3-7 Sweep Marker and Sync Outputs ............................................. 3-15
Figure 3-8 Relational Range for Allowed AC Amplitude Voltage and DC Offset Voltage ............ 3-25
Figure 3-9 PhaseRelationship Between Waveform and Synchronous Output ..................... 3-27
Figure 3-10 BURSTOscillation ........................................................ 3-28
Figure 3-l 1 TriggerOscillation ........................................................ 3-29
Figure 3-12 GateOscillation .......................................................... 3-29
Figure 3-13 Waveforms and PhaseDefinitions ............................................. 3-31
Figure 3-14 Waveform Examples with Hold Stop Level ...................................... 3-32
Figure 3-15 Waveform Examples with ResetStop Level ...................................... 3-32
Figure 3-16 PhaseSync Operation ...................................................... 3-33
Figure 3-17 PhaseRelationship after PhaseSync ............................................ 3-33
Figure 3-18 Sweep Frequency and Sweep Output ........................................... 336
Figure 3-19 SweepOperation ......................................................... 3-37
SECTION 4 - GPIB Interface
Figure 4-l Interface Connector ....................................................... 4-2
Figure 4-2 Handshake Timing Diagram ................................................. 4-3
Figure 4-3 Data Transfer Example ..................................................... 44
Figure 4-4 Program Code Syntax ...................................................... 4-7
Figure 45 ResponseOutput Format ................................................... 4-9

List of Tables
SECTION 2 - Getting Started
Table 2-l FuseReplacement......................................................... 2-3
SECTION 3 - Operation
Table 3-l Main Synthesizer Amplitude Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
Table 3-2 Sub Synthesizer Amplitude Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
SECTION 4 - GPIB Interface
Table 4-l Multi-Line Interface Messages ................................................ 4-5
Table 4-2 InterfaceFunctions.. ...................................................... 4-6
Table 4-3 BusDriverSpecifications ................................................... 4-6
Table 4-4 Responsesto Interface Messages .............................................. 4-7
Table 4-5 StatusByte.. ............................................................ 412
Table 4-6 Main Synthesizer Parameter Setting Messages .................................... 4-13
Table 4-7 Sub Synthesizer Parameter Setting Messages ..................................... 4-16
Table 4-8 Main Synthesizer Trigger Parameter Setting Messages .............................. 4-18
Table 4-9 Main Synthesizer Sweep Parameter Setting Messages .............................. 420
Table 4-10 Miscellaneous Parameter Messages ............................................ 4-23
Table 4-l 1 ARB Waveform Write and Readout Messages .................................... 4-24
Table 412 Parameters Specific to GPIB ................................................. 4-25
Table 4-13 Main Synthesizer Parameter Inquiry Messages ................................... 4-26
Table 4-14 Sub Synthesizer Parameter Inquiry Messages .................................... 4-28
Table 4-15 Main Synthesizer Trigger Parameter Inquiry Messages ............................. 4-29
Table 416 Main Synthesizer Sweep Parameter Inquiry Messages .............................. 4-30
Table 4-l 7 Inquiry Messagesfor Miscellaneous Parameters .................................. 4-32
Table 4-18 Inquiry Messagesfor ARB Waveform Write and Readout Parameters .................. 4-33
Table 4-19 Inquiry Messagesfor Parameters Specific to GPIB ................................. 434
Table 420 Typical Execution Times .................................................... 4-35
Table 4-21 Program Codes Summary ................................................... 4-40

SECTION 1
General Information
1.l INTRODUCTION
The Model 3940 Multifunction Synthesizer is a multi-
function oscillator integrated with two frequency synthe-
sizers: the OHzto 2OMHz main synthesizer and the OHz
to 1OOkHzsub synthesizer. The Model 3940can generate
the entire frequency band at aresolution of O.lmHz, with
an accuracy of tippm.
Five output waveforms, %,%,-rL,n,and\,are
available. In addition, arbitrary waveforms set with the
GPlB (IEEE-4881interface can be generated by the main
synthesizer. Maximum output voltage for all waveforms
is 20V p-p (no load).
Since frequencies are synthesized directly by a custom
LSI digital IC, accuracy and stability arehigh, and the fre-
quency switching time is short. Mother advantage is the
continuity of phase at frequency switchover.
Frequency sweep, half-cycle unit bursts of up to 32,768
cycles, trigger oscillation, and gate oscillation are avail-
able with the main synthesizer. The square-wave duty
cycle is also variable. In addition, external signals can be
combined with the oscillator output to generate custom
waveforms.
Frequency, amplitude, waveform, and phase can be in-
dependently set on the sub synthesizer, which is not de-
pendent upon the main synthesizer. The sub synthesizer
can also be used asa trigger oscillator for the main syn-
thesizer.
Since the sub synthesizer and the main synthesizer use
the same clock source, the phase will not deviate when
the frequency is setwith a whole number ratio.
The Model 3940usesatwo-line, 40-character liquid crys-
tal display to display selectedfunctions, parameters, and
pertinent messages.Parameter settings are easily made
using both the numeric keys and the modify knob.
The Model 3940 is equipped with a standard GPIB
(IEEE-4881interface, and can be programmed over the
bus for the same operating modes and parameters that
can be controlled from the front panel.
The Model 3940 can be used as a multiphase oscillator
when combined with multiple identical units and used
with the optional synchronous cable.
1.2 FEATURES
1. Two integrated independent frequency synthesiz-
ers:Main Synthesizer and Sub Synthesizer
l-l