Keithley 3940 User manual

9 ultif unctio
mice mud
ontains Servicing Information
Publication Date: August 1991
Document Number: 3940-902-01 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 of shipment: probes, cables,
rechargeable batteries, diskettes, and documentation.
During the warranty period, we will, at our option, either repair or replace any product that proves to be de-
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 bemade and the product returned, transportation
prepaid. Repaired or replaced products are warranted for the balance of the original warranty period, or at
least 90 days.
LIMITATION OF WARRANTY
This warranty 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 IS IN LIEU OF ALL OTHER WARRANT IES,EXPRESSEDOR IMPLIED, INCLUDING
ANY IMPLIED WARRANTY OF MERCHANTABILITY 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.
INSTRUMENT-S
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WF.ST GERMANY:
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Service Manual
Model 3940
Multifunction Synthesizer
01991, Keithley Instruments, Inc.
All Rights Reserved
Instruments Division
Cleveland, Ohio, U. S.A.
Document Number: 3940-902-01

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 each use.
For maximum safety, do not touch the test cables or any instruments while power is applied to the circuit under test.
Turn off the power and discharge any capacitors before connecting or disconnecting cables from 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.

HOW TO USE THIS MANUAL
Details procedures to verify that the instrument meets
stated specifications.
SECTION 1
Performance Verification
Describes basic operating principles for the various circuits in
SECTION 2
the Model 3940.
Principles of Operation
Covers fuse replacement, calibration and repair of the instru-
SECTION 3
ment, and lists replacement parts.
Service Information
WARNING
The information in this manual is intended for qualified serv-
ice personnel who can recognize possible shock hazards. Do
not attempt these procedures unless you arequalified to do so.

Table of Contents
SECTION 1 - Performance Verification
1.1 INTRODUCTION. ............................................................. l-l
1.2 ENVIRONMENTAL CONDITIONS ................................................ l-l
1.3 INITIALCONDTMONS ......................................................... l-l
1.4 LINEPOWERVOLTAGE.. ...................................................... l-1
1.5 RECOMMENDED TESTEQTJIPMENT .............................................. l-l
1.6 VERIEXATION PROCEDURES ................................................... l-2
1.6.1 Frequency and Duty Cycle Accuracy .............................................. l-2
1.6.2 AmplitudeAccuracy .......................................................... l-4
1.6.3 Frequency Response (Sine) ..................................................... 1-6
1.6.4 Frequency Response (Triangle, Sawtooth, Square) .................................... l-7
1.6.5 Frequency Response (Sub Sine) ............................ :. .................... l-8
1.6.6 Total Harmonic Distortion ..................................................... 1-8
1.6.7 DCVoltageAccuracy ......................................................... l-10
1.6.8 DCLevel(Square)andDCOffsetError(Sine) ....................................... l-11
SECTION 2 - Principles of Operation
2.1 INTRODUCTION .............................................................. 2-l
2.2 BLOCKDIAGRAM ............................................................ 2-1
22.1 ControlSection .............................................................. 2-1
2.2.2 Display and Keyboard Section ................................................... 2-1
2.2.3 Trigger Section .............................................................. 2-1
2.2.4 SweepSection ............................................................... 2-1
2.2.5 GMBInterface ............................................................... 2-l
2.2.6 SubSynthesizer ............................................................. 2-3
2.2.7 MainSynthesizer ............................................................ 2-3
2.2.8 PowerSupply ............................................................... 2-3
2.3 MAINSYNTHESIZERDESCRIl?TION .............................................. 2-3
2.3.1 Main Synthesizer Block Diagram ................................................. 2-3
2.3.2 D/AConverter .............................................................. 2-3
2.3.3 SquareWaveGenerator ....................................................... 2-3
2.3.4 Amplitude Control ........................................................... 2-3
2.3.5 OutputAmplifier ............................................................ 2-3
2.3.6 Calibration ................................................................. 23
2.4 SYNTHESIZER OPERATING PRINCIPLES .......................................... 2-5
SECTION 3 - Service Information
3.1 INTRODUCTION .............................................................. 3-1
3.2 LINEFUSEREPLACEMENT ..................................................... 3-1
3.3 CALIBRATION ............................................................... 3-1
3.3.1 EnvironmentalConditions ..................................................... 3-2

3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.3.7
3.3.8
3.4
3.5
3.6
3.6.1
3.6.2
3.6.3
3.7
3.7.1
3.7.2
InitialConditions ............................................................
LinePower............., ...................................................
Recommended Calibration Equipment ............... ; .............................
Cover Removal ..............................................................
CalibrationAdjustments.. .....................................................
CalibrationProcedures ........................................................
CoverReplacement ...........................................................
FANFILTERCLEANING ........................................................
RECHARGEABLE BATTERY REPLACEMENT ........................................
REPAIR .... .................................................................
Factory Service ..............................................................
PowerSupplyTestPoints ......................................................
Board-LevelRepair ...........................................................
REPLACEABLEPARTS .........................................................
PartsList ..................................................................
OrderingParts ..............................................................
APPENDICES
A Typical Data
B Model 3940Specifications
3-2
3-2
3-2
3-2
3-3
3-6
3-8
3-9
3-9
3-9
3-9
3-9
3-11
3-11
3-11
3-11

List of Illustrations
SECTION 1 - Performance Verification
Figure l-l
Figure l-2
Figure l-3
Figure l-4
Connections to Timer/Counter ............................................... l-3
ConnectionstoModel197ADMM ............................................ l-4
Connections to Wideband AC DVM ........................................... l-6
Connections to Audio Analyzer .............................................. l-9
SECTION 2 - Principles of Operation
Figure 2-l
Figure 2-2
Figure 2-3
Figure 2-4
Figure 2-5
Overall Block Diagram ..................................................... 2-2
Main Synthesizer Block Diagram .............................................. 2-4
Frequency Synthesizer Address Generator Diagram .... ........................... 2-5
Address Generator Waveform ...... ......................................... 2-6
Waveform Memory and D/A Converter ........................................ 2-6
SECTION 3 - Service Information
Figure 3-1
Figure 3-2
Figure 3-3
Figure 3-4
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9
CoverRemoval ........................................................... 3-3
Analog Board (NP-10375) Calibration Adjustments ................................ 3-4
Control Board (NP-21007) Calibration Adjustments ................................ 3-5
Sub Synthesizer Output Connections to Model 197A DMM .......................... 3-6
Main Synthesizer Output Connections to Timer/Counter ........................... 3-7
Main Synthesizer Output Connections to DMM .................................. 3-7
DMM Connections to DC OFSand GND Test Points ............................... 3-8
Power Supply Test Points ................................................... 3-10
Model 3940Exploded View .................................................. 3-12

List of Tables
SECTION 1 - Performance Verification
Table l-1 Verification Equipment ..................................................... 1-2
Table l-2 Limits for Frequency and Duty Cycle Accuracy ................................... l-3
Table 1-3 Limits for Amplitude Accuracy ............................................... 1-5
Table 1-4 Limits for Frequency Response (Sine) .......................................... 1-7
Table 1-5 Limits for Frequency Response (Triangle, Sawtooth, Square) .......................... 1-7
Table l-6 Limits for Frequency Response (Sub Sine) ....................................... 1-8
Table 1-7 Limits for Total Harmonic Distortion .......................................... l-10
Table l-8 Limits for DC Voltage Accuracy .............................................. l-10
Table l-9 LimitsforDCLevel(Square)andDCOffsetError(Sine) ............................ l-11
SECTION 3 - Service Information
Table 3-l Recommended Line Fuses ................................................... 3-1
Table 3-2 Recommended Test Equipment for Calibration ................................... 3-2
Table 3-3 Board Level Repair Summary ................................................ 3-11
Table 3-4 Replaceable Parts ......................................................... 3-l 1

SECTION1
Performance Verification
1.I INTRODUCTION
The procedures outlined in this section may be used to
verify that the instrument is operating within the limits
stated in the specifications. Performance verification may
be done when the instrument is first received to ensure
that no damage or misadjustment has occurred during
shipment. Verification may also beperformed whenever
there is a question of instrument accuracy, or following
calibration, if desired.
procedures. If the instrument has been subjected to ex-
tremes of temperature (outside the range specified in the
previous paragraph), additional time should be allowed
for internal temperatures to reach normal operating tem-
perature. Typically, it takes one additional hour to stabi-
lize a unit that is 10°C (18“F) outside the specified tem-
perature range.
1.4 LINE POWER VOLTAGE
NOTE
If the instrument is still under warranty (less
than one year from the date of shipment), and
its performance falls outside the specified
Before performance verification, be sure the line voltage
selector switch setting is setto the correct position. Tests
should be performed with the instrument operating on a
line voltage within 10%of the setvoltage and ataline fre-
quency from 48 to 62Hz.
. A
range, contact your Keithley representative or
the factory to determine the correct course of
1.5 RECOMMENDED TEST EQUIPMENT
action.
1.2 ENVIRONMENTAL CONDITIONS
Table l-1 lists all the test equipment needed for verifica-
tion. The procedure for performance verification isbased
on using this exact equipment.
All measurements should be made at 18-28°C (65-82’F)
and at lessthan 70%relative humidity.
1.3 INITIAL CONDITIONS
NOTE
The verification limits reflect only the accu-
racy specifications of the Model 3940.They do
not include test equipment tolerance.
The Model 3940must beturned on and allowed to warm
up for at least one hour before beginning the verification
Alternate equipment may be used aslong asthe substi-
tute equipment has specifications at least as good as
those listed in Table l-l.
l-l

SECTION 1
PerformanceVerification
Table l-l. Verification Equipment
Manufacturer
Keithle y
Fluke
Philips
Panasonic
Keithley
Keithley
Pomona
Model
197A
8920A
PM 6654C
PM 9678
VP-7722A
7051-2
7755
1468
Description
DMM (DC volts, AC volts)
(5-l/2 digits)
DVM (AC volts)
(3-l /2 digits)
Timer/Counter
TCXO option
Audio Analyzer
BNC Interconnect Cable
5OQFeed-through Terminator
BNC-banana Adapter
1.6 VERIFICATION PROCEDURES 1.6.1
The following paragraphs contain the detailed proce-
dures for verifying accuracy specifications of the Model
3940using the equipment listed in Table l-l. The allow-
able reading limits in theseprocedures do not include er-
ror that could be contributed by this equipment.
These procedures are intended for use only by qualified
personnel using accurate and reliable test equipment. If
the instrument is out of specifications and not under war-
ranty, refer to the calibration information in Section 3.
Specifications
20V range; ~t(O.O15%of rdg + 3 counts)
ACV; &(0.35%of rdg + 100counts)
20V range; lkHz-200kHz (0.5%of rdg),
2OOkHz-1MHz (0.7%),l-1OMHz (3%),lo-2OMHz (5%)
O.OlHz-12OMHz;time baseaging
<1 x lO-‘/month; Vp-p measurements
lOHz-11OkHz; 0.001%at full scale;rtldB harmonic
distortion accuracy from 1OHzto 15.99kHz
5OQcoaxial cable (RG-58C),male BNC connectors,
2ft (0.6m)
BNC to BNC adapter, 5OQtermination, DC to
25oMHz, VSWR of cl.1
Female BNC connector to double banana plug
Frequency and Duty Cycle
Accuracy
1. Connect the function synthesizer to atimer/counter
asshown in Figure l-1. Turn on both instruments.
2. Restorefactory defaults on the Model 3940by press-
ing SHIPT PRST.
3. Program a 1OMHz sine function of 2OVp-p.
4. Set the tuner/counter to display the frequency at
Channel A, and verify that the frequency reading is
within the limits specified in Table 1-2.
5. Program a1kHz square wave with afixed 50%duty
cycle.
6. Setthe timer/counter to display the pulse width of
Channel A, and verify that the reading is within
specifications.
7. Modify the frequency and duty cycle settings of the
main synthesizer according to Table 1-2 and verify
the pulse width readings.
l-2

SECTION 1
PerformanceVerification
Model 3940
Fipure 2-l.
NOTE : Set Timer/Counter
for 5Oa Input
Connectionsto Timer/Counter
Table 1-2. Limits for Frequency and Duty Cycle Accuracy
Allowable Reading
Synthesizer Function Amplitude Frequency (18T to 28W
Main Sine 2ovp-p 1OMHZ 9.99995M.a to 10.00005MH2
M&l Square (FKD50) 2ovp-p 1kHZ
498.5psec to 501.5pec
lOk?sz 49.85psec to 50.15pec
1OOkHz 4.985psec to 5.015pec
500kHz 0.98psec to 1.02pec
1MHz 490nsec to 5lOnsec
Main Square (VAR 5) 2ovp-p 1kHz 49.5pec to 50.5j.isec
(VAR50) 495psec to 505pec
(VAR95) 940.5psec to 959.5pec
Main Square (VAR50) 2OVp-p 1okHz 49.5pec to 50.5ysec
1ookJrIz 4.95psec to 5.05ysec
5ookJrIz 0.99pec to l.Olp.sec
lh4Hz 495nsec to 505nsec
l-3

Sh7ON 1
PerformanceVerification
1s.2 Amplitude Accuracy
1. Connect the function synthesizer to a DM&i as
shown in Figure l-2A. Turn on both instruments.
2. Restorefactory defaults on the Model 3940by press-
ing SHIFT PRST.
3. Program a 1kHz sine function of 2OVp-p.
4. Setthe DMM to measure AC volts with autoranging,
and verify that the voltage reading is within the lim-
its specified in Table l-3.
5. Change the function, frequency, and amplitude set-
tings of the main and sub synthesizers according to
Table 13, and verify the voltage readings. When
verifying subsynthesizer accuracy, switch the coax-
ial cableto the subsynthesizer function out jack. (See
Figure l-2B.)
Model 3940
A. Main Synthesizer
Model 3940
Model 197A DMM
Sub
Function
output
B. Sub Synthesizer
Fimtrel-2. ConnecfionsfoModel 197A DMM
l-4

SECTION 1
PerformanceVerification
Table l-3. Limits for Amplitude Accuracy
Synthesizer
Main
Main
Sub
Main
Main
Main
Sub
Function Frequency
Sine 1kHZ
1okHz
Sine 1kHz
Sine 1kHZ
Triangle 1kHz
Square (VAR50) lkJ&
uxD50)
Sawtooth Up 1kHZ
Sawtooth Down
Triangle 1kHZ
Square
Sawtooth Up
Sawtooth Down
Amplitude
2o.ovp-p
15.ovp-p
11.3vp-p
11.2vp-p
6.29Vp-p
3.55vp-p
2.OlVp-p
2.oovp-p
2OOmVp-p
2o.ovp-p
15.ovp-p
lO.OVp-p
5.oovp-p
2o.ovp-p
2o.ovp-p
2o.ovp-p
2o.ovp-p
Allowable Reading
(18T to 28W
6.9297Vrms to 7.2124Vrms
6.9297Vrms to 7.2124Vrms
5.1973vrms to 5.4093vrIns
3.9153vrms to 4.075ovrms
3.8807Vrms to 4.0389Vrms
2.1794Vrms to 2.2683Vrms
1.23OlVrms to 1.2802vrms
0.6965Vrms to 0.7248Vrm
0.6789Vrms to 0.7353Vrms
0.0665Vrms to 0.0749Vrms
6.859OVrms to 7.2831Vrms
5.1443Vrms to 5.4623Vrms
3.4295vms to 3.6415vrms
~1.7148Vrms to 1.8207Vrms
5.6003Vrms to 5.9467Vrms
9.8OVrms to 10.2vrms
9.80Vrms to 10.2vrms
5.6003Vrms to 5.9467Vrms
5.6003Vrms to 5.9467Vrms
5.6003Vrms to 5.9467Vrms
9.7vrms to 10.3vrms
5.6003Vn.n~ to 5.9467Vrms
5.6003Vrms to 5.9467Vrms
l-5

SECTION 1
PerformanceVerification
1.6.3 Frequency Response (Sine)
4. Setthe DVM to measure AC volts with autoranging,
and verify that the voltage reading is within the lim-
its specified in Table 14.
1. Connect the function synthesizer to awideband AC 5. Setihe DVM to measure dB and select a 5022refer-
DVM asshown in Figure l-3A. Turn on both instru- ence impedance. PressREL to establish the present
ments. voltage reading asthe relative dB reference.
2. Restorefactory defaults on the Model 3940by press-
ing SHIFT’PRST. 6. Change the frequency setting of the main synthe-
sizer according to Table 1-4, and verify the subse-
3. Program a 1kHz sine function of 2OVp-p. quent fdB readings.
Figurel-3.
Model 3940
Main ’ 1
Function
output Coaxial Cable
Model 7755
5on
Feed Through
Model 8920A DVM
A. Main Synthesizer
Model 3940
Model 8920A DVM
Sub
Function
output
B. Sub Synthesizer
Connectionsfo WidebandAC DVM
l-6

SECTlON 1
PerformanceVerification
Table 1-4. Limits for Frequency Response (Sine)
Svnthesizer
Main
Function
Sine
Amplitude
~ 2ovp-p
Frequency
1kHZ 34649Vrms to 3.6062Vrms (=REF)
1ookHz +0.3dB to -0.3dB
MHZ +0.3dB to -0.3dB
2MHz +0.3dB to -0.5dB
3.5MHz +0.3dB to -0.5dB
5MHz +0.3dB to -0.5dB
mz +0.3dB to -0.5dB
1oMHz +0.3dB to -1 .OdB
15MHz +0.3dB to -2.5dB
2oMHz +0.3dB to -2.5dB
Allowable Reading
mPc to 28w
1.6.4 Frequency Response (Triangle,
Sawtooth, Square)
1. Connect the function synthesizer to atimer/counter
asshown in Figure l-l. Turn on both instruments.
2. Restore factory defaults on the Model 3940by press-
ing SHIFT PRST.
3. Program a 1kHz triangle wave of 18Vp-p.
4. Set the timer/counter to display the peak-to-peak
voltage at Channel A, and verify that the voltage
reading is within the limits specified in Table l-5.
Call this reading REF.
5. Change the frequency to 5OkHz. The new reading
should be between 0.97 times the REF reading and
1.03times the REFreading.
6. Modify the frequency and function settings of the
main synthesizer according to Table l-5 and verify
that the corresponding readings arewithin the speci-
fied limits.
Table 1-5. Limits for Frequency Response (Triangle, Sawtooth, Square)
Synthesizer
Main
Main
Main
Main
Function
Triangle
Amplitude
18Vp-p
Sawtooth Up 18Vp-p
Sawtooth Down 18Vp-p
Square
Frequency
I
Allowable Reading
(18°C to 28°C)
1kHZ
5okHz
_^^. --
IUUkHZ
8.73Vp-p to 9.27Vp-p (=REFI
0.97xREF to 1.03xRRF
^ ^W w-w
u.!u xKJ2r to ” -- ---1.w x lus
1kHZ 8.73Vp-p to 9.27Vp-p (=REF)
5okHz 0.95xREF to 1.05xRRF
1ookHz 0.95xRRF to 1.05xREF
1kHZ 8.73Vp-p to 9.27Vp-p (=REF)
5okHz 0.95xRRF to 1.05xREF
1OOkHZ 0.95xRRF to 1.05xREF
&Hz
501612
1ookHz
lMH7L
8.82Vp-p to 9.18Vp-p (=REF)
0.97xRRF to 1.03xREF
0.97xREF to 1.03xREF
0.97RRF to 1.03x REF

SECTION 1
PerformanceVerification
1.6.5 Frequency Response (Sub Sine) 1.6.6 Total Harmonic Distortion
1. Connect the function synthesizer to awideband AC
DVM asshown in Figure 13B. Turn on both instru-
ments.
2. Restorefactory defaults on the Model 3940by press-
ing SHIPI’ PRST.
3. Program a 1kHz sine function of 2OVp-p.
4. Setthe DVM to measure AC volts with autoranging,
and verify that the voltage reading is within the Iim-
its specified in Table l-6.
5. Setthe DVM to measure dB and select a 5OQrefer-
ence impedance. PressRRL to establish the present
voltage reading asthe relative dB reference.
6. Change the frequency setting of the sub synthesizer
according to Table l-6, and verify the subsequent
rtdB readings.
1. Connect the function synthesizer to an audio ana-
lyzer asshown in Figure 1-4A. Turn on both instru-
ments.
2. Restorefactory defaults on the Model 3940by press-
ing SHIFT PRST.
3. Program a 1kHz sine function of 2OVp-p.
4. Set the audio analyzer to measure distortion, and
verify that the reading is within the limits specified
in Table l-7.
5. Change the frequency setting of the main and sub
synthesizers according to Table l-7, and verify the
distortion readings. When verifying subsynthesizer
distortion, switch the coaxial cable to the subsyn-
thesizer function out jack. (SeeFigure 1-4B.)
Table 1-6. Limits for Frequency Response (Sub Sine)
Synthesizer I Function I Amplitude I Frequency
I
Allowable Reading
(18T to 28’C)
Sub Sine 2ovp-p 6859OVrms to 7.2831Vrms (=REF)
+0.3dB to -0.3dB
+0.3dB to -0.3dB
+0.3dB to -0.3dB
+l.OdB to -2.OdB
+l.OdB to -2.OdB
l-8

SECTION 1
PerformanceVerificafion
Model 3940 Model VP-7722A Audio Analyzer
Input
Moael7051-2 L;oaxfal C;aot
. . ..- --.- - ..-..
Note: Put FLT Switch
in ground position
A. Main Synthesizer
Sub
Function
output
Note: Put FLT Switch
in ground position
B. Sub Synthesizer
Figure l-4. ConnecfionstoAudio Analyzer
l-9

sEcz7oN 1
PerformanceVerification
Table 1-7. Limits for Total Harmonic Distortion
,
Sub
Allowable Reading
Synthesizer Function Amplitude Frequency mPc to 28W
Main Sine 2ovp-p 1kHk < 0.3%
IOkHZ < 0.3%
2okHz < 0.3%
35kHz < 0.3%
5okHz < 0.3%
7okHz < 0.3%
1ookHz < 0.3%
Sine aovp-p
1kHZ < 0.2%
5kHz < 0.2%
1okHz < 0.3%
20kHz < 0.3%
35kHz < 0.3%
5okHz < 0.3%
70kHz < 0.3%
1ookHz < 0.3%
1.6.7 DC Voltage Accuracy
1. Connect the function synthesizer to a DMM as
shown in Figure l-2A. Turn on both instruments.
2. Restorefactory defaults on the Model 3940by press-
ing SHIFT PRST.
3. Program the DC function, OHz,2.OOmVamplitude,
with +lO.OVoffset.
4. Setthe DMM to measure DC volts with autoranging,
and verify that the voltage reading is within the lim-
its specified in Table 1-8.
5. Change the offset setting of the main synthesizer ac-
cording to Table l-8 and verify the subsequent volt-
agereadings.
Table l-8. Limits for DC Voltage Accuracy
Synthe- Allowable Reading
sizer Function Offset mot to 28°C)
Main DC +lO.OV
-1o.ov
+5.oov
-5.oov
+2.5OV
-2.5OV
+l.OlV
-1.OlV
9.88V
to 10.12v
-9.88V to -10.12v
4.93v to 5.07V
-4.93v to -5.07V
2.455V to 2.545V
-2.455V to -2.545V
0.9799v to 1.0401v
-0.9799v to -1.0401v
l-10

SECTION 1
PerformanceVerificafion
1.6.8 DC Level (Square) and DC Offset
Error (Sine)
4. Setthe DMM to measure DC volts with autoranging,
and verify that the voltage reading is within the lim-
its specified in Table l-9.
trigier source,Akd +bO”phase.. v function out jack. (SeeFigure l-2B.)
Table 1-9. Limits for DC Level (Square) and DC Offset Error (Sine)
1. Connect the function synthesizer to a DMM as
shown in Figure 1-a. Turn on both instruments.
2. Restorefactory defaults on the Model 3940by press-
ing SHIFT PRST.
3. Promam a2OVp-Psquare wave, nated mode, Ext %.
5. ChAge the function, amplitude, mode, trigger
source, and phase settings of the main and sub syn-
thesizers according to Table l-9, and verify the volt-
age readings. When verifying subsynthesizer accu-
racy, switch the coaxial cable to the subsynthesizer
Synthesizer
Main
Main
Sub*
Function
Square
Sine
Sine
Amplitude
2ovp-p
2ovp-p
IL.OlVp-p
2.oovp-p
2.oovp-p
Mode
Gate
Gate
Cont.
Trigger
Source
Extk
Ex&
Intx
Phase
+90”
-90”
O0
O0
Allowable Reading
(WC to 28W
9.8V to 10.2v
-9.w to -10.2v
fl2OmV
f3OmV
tiOmV
i2OmV
* Note: Function Out is OFF for Sub Synthesizer test.
l-11