Tektronix 7S11 User manual

Tektronix, Inc.
It!ktron~
COMMITTED TO EXCELLENCE
WARNING
THE FOLLOWING SERVICING INSTRUCTIONS
ARE FOR USE BY QUALIFIED PERSONNEL
ONLY. TO AVOID PERSONAL INJURY,
DO NOT
PERFORMANYSERVICING OTHERTHANTHAT
CONTAINED
IN OPERATING INSTRUCTIONS
UNLESS YOU ARE QUALIFIED TO
DO SO.
PLEASE CHECK FOR CHANGE INFORMATION
AT THE REAR OF THIS MANUAL.
7S11
SAMPLING
UNIT
INSTRUCTION MANUAL
P.O. Box 500
Beaverton,Oregon 97077 Serial Number:
____ _
070-0985-00
Product Group 42
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First Printing FEB 1970
Revised FEB 1989

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Copyright @ 1970 Tektronix, Inc. All rights reserved.
Contents
of this publication may not be reproduced in any
form without the written permission
of Tektronix, Inc.
Products of Tektronix, Inc. and its subsidiaries are covered
by U.S. and foreign patents and/or pending patents.
TEKTRONIX, TEK, SCOPE-MOBILE, and
~ are
registered trademarks
of Tektronix, Inc. TELEQUIPMENT
is a registered trademark
of Tektronix U.K. Limited.
Printed
in U.S.A. Specification and price change privileges
are reserved.
INSTRUMENT SERIAL NUMBERS
Each instrument has a serial number on a
pa~el insert, tag,
or stamped on the chassis. The first number
or letter
deSignates the country of manufacture. The last five digits
of the serial number are assigned sequentially and are
unique to each instrument. Those manufactured
in the
United States have six unique digits. The country
of
manufacture is identified as follows:
BOOOOOO
100000
200000
300000
700000
Tektronix, Inc., Beaverton, Oregon, USA
Tektronix Guernsey, Ltd., Channel Islands
Tektronix United Kingdom, Ltd., London
Sony/Tektronix, Japan
Tektronix Holland, NV, Heerenveen,
The Netherlands
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TABLE OF CONTENTS
SECTION 1 SPECIFICATION Page
General Information
1-1
Electrical 1-1
Environmental
Characteristics
1-2
Physical
Characteristics
1-2
SECTION 2 OPERATING INSTRUCTIONS
General Information
2-1
Installation 2-1
Mating 2-1
First- Time Operation 2-2
Equivalent- Time Sampling Operation 2-2
Controls and Connectors 2-2
Basic Operating Information 2-2
Basic Applications
2-9
WARNING'
THE FOLLOWING SERVICEINSTRUCTIONS ARE FOR USE BY QUALIFIED PERSONNEL
ONLY. TO AVOID PERSONAL INJURY, DO NOT PERFORM ANY SERVICING OTHER
THAN THAT CONTAINED IN OPERATING INSTRUCTIONS UNLESS
YOU ARE QUALI-
FIED
TO DO So.
SECTION 3 BASIC SAMPLING PRINCIPLES
Introduction
3-1
Basic Sampling Techniques 3-1
Effective Sampling Time
3-4
Traveling Wave Sampling Gate 3-5
Dot Response (Loop Gain) 3-5
Smoothing 3-5
Smoothing of Random Noise 3-6
Tangential Noise
3-6
Display Sensitivity-Deflection Factor
3-7
DC Offset
3-7
Real-Time
Sampling
3-8
Sweep Rates 3-8
REV FEB 1984
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7811
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7S11
TABLE
OF CONTENTS
(cont)
SECTION 4 CIRCUIT DESCRIPTION Page
Introduction 4-1
Block Diagram 4-1
Feedback Loop and Pulse Amplifier Chain 4-1
Vertical
Output Amplifier
4-1
Sweep Unit Drive 4-1
Readout
Logic 4-3
Circuit Description 4-3
Trigger Logic 4-3
Post Amplifier and Attenuators 4-3
Memory 4-5
Output Amplifier 4-8
Real
Time Oscillator 4-8
Gate Generator 4-9
Readout LogiC 4-11
Power
Distribution and Decoupling 4-11
SECTION 5 MAINTENANCE
Introduction 5-1
Preventive Maintenance 5-1
General 5-1
Cleaning 5-1
Lubrication 5-1
Visual
Inspection 5-1
Calibration 5-1
Parts
Identification
5-1
Parts
Replacement
5-2
Troubleshooting
5-4
Introduction 5-4
Troubleshooting Aids 5-4
Troubleshooting Techniques 5-5
Transistor Checks 5-5
Diode Checks
5-5
Field Effect Transistors (FET) 5-6
Repackaging for Shipment
5-7
SECTION 6 PERFORMANCE CHECK/CALIBRATION
Introduction
6-1
Test
Equipment Required 6-1
Short Form
Procedure
6-2
Preliminary Procedure 6-3
Check -12.2-Volt Power Supply
6-5
Check Interdot Blanking
6-6
Check Dot Response and Smooting
6-7
Adjust Memory Gate Width (R460) and
Memory Gain (C275) With Normalizer Head 6-7
Adjust Memory Gate Width (R460) and
Memory Gain (C275) With Sampling Head 6-8
ii
REV FEB 1984
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REV FEB 1984
TABLE OF CONTENTS (cont)
SECTION 7
SECTION 8
SECTION 9
Adjust Variable Balance (R30S) and
Smooting Balance (R24S)
Check Deflection Factor Accuracies,
Variable Control Range and Adjust GAIN
Check Memory Overdrive Recovery
Check Vertical Signal Out
Check Vertical Gain Change in SMOOTH
Check Memory Slash
Check Delay
Check/Adjust Real Time Sampling (R41S)
Check DC Offset and Adjust Position (R32S)
Check Real-Time Trigger Amplifier Output
ELECTRICAL PARTS LIST
Abbreviations and Symbols
Parts Ordering Information
Index of Electrical Parts List
Electrical Parts List
DIAGRAMS AND MECHANICAL PARTS ILLUSTRATIONS
Diagrams
Mechanical Parts Illustrations
Repackaging Instructions
MECHANICAL PARTS LIST
Mechanical Parts List Information
Index of Mechanical Parts Illustrations
Mechanical Parts List
Accessories
CHANGE INFORMATION
Page
6-9
6-10
6-11
6-11
6-11
6-11
6-12
6-12
6-12
6-14
Abbreviations and symbols used in this manual are based on or taken di-
rectly from IEEE Standard 260 "Standard Symbols for Units", MIL-STD-12B
and other standards of the electronics industry. Change information, if any,
is located at the rear of this manual.
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7511
iii
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7S11
SAFETY SUMMARY
The general safety information contained in this summary is for servicing personnel. Specific warnings and cautions will be
found throughout the manual where they apply, but may not appear in this summary.
TERMS
IN THIS MANUAL
CAUTION statements identify conditions or practices that could result in damage to the equipment or other property.
WARNING statements identify conditions or practices that could result
in personal injury or loss of life.
AS MARKED ON EQUIPMENT
CAUTION indicates a personal injury hazard not immediately accessible as one reads the marking, or a hazard to property
including the equipment itself.
DANGER indicates a personal injury hazard immediately accessible as one reads the marking.
SYMBOLS
IN THIS MANUAL
® Static-Sensitive Devices
This symbol indicates where applicable cautionary or other information is to be found.
AS MARKED ON EQUIPMENT
DANGER-High voltage.
Protective ground (earth) terminal.
ATTENTION-refer to manual.
WARNINGS
POWER SOURCE
This product is intended to operate from a power source that will not apply mare than 250 volts rms between the supply
conductors or between either supply conductor and ground. A protective ground connection by way of the grounding conduc-
tor
in the power cord is essential for safe operation.
USE THE PROPER POWER CORD
Use only the power cord and connector specified for your product. Use only a power cord that is in good condition.
GROUNDING THE PRODUCT
This product is grounded through the grounding conductor of the power cord. To avoid electrical shock, plug the power cord
into a properly wired receptacle before making connections to the product input or output terminals. A protective ground
connection
by way of the grounding conductor in the power cord is essential for safe operation.
iv ADD FEB 1984
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7511
DANGER ARISING FROM LOSS OF GROUND
Upon loss of the protective-ground connection, all accessible conductive parts (including knobs and controls that may appear
to
be insulating), can render an electric shock.
USE THE PROPER FUSE
To avoid hazard, use only the fuse specified in the parts list for your product, and which is identical in type, voltage rating, and
current rating.
DO NOT OPERATE IN EXPLOSIVE ATMOSPHERES
To avoid explosion, do not operate this product in an atmosphere of explosive gases unless it has been specifically certified for
such operation.
DO NOT SERVICE ALONE
Do not perform internal service or adjustment of this product unless another person capable of rendering first aid and
resuscitation is present.
USE CARE WHEN SERVICING WITH POWER ON
Dangerous voltages exist at several pOints in this product. To avoid personal injury, do not touch exposed connections and
components while power
is on.
Disconnect power before removing protective panels, soldering, or replacing components.
SILICONE GREASE HANDLING
Handle silicone grease with care. Avoid getting the silicone grease in your eyes. Wash hands thoroughly after using silicone
grease.
ADD FEB 1984 v
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-
DElAV
' ...... "#Io H QII
•. ~
, .. ..-.
SAMPUNO UNIT
7511
Fi9. 1·1. 7511 Sim pli ng Unit.
ScOffS by ARTEK MEDIA ->
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7811
SECTION 1
7S11 SPECIFICA TION
Change information, if any, affecting this section will be found at the rear of the manual.
General Information
The 7S11 Sampling Unit is a single channel vertical
amplifier plug-in
unit designed for operation in Tektronix
7000-Series Oscilloscopes. The 7S11 accepts the S-Series
Sampling Heads. The Sampling
Head determines the input
characteristics and the availability of a trigger pickoff.
The S-Series Sampling Head used can be plugged into the
7S11 or used remotely on an optional extender cable unit.
The 7S11 provides the power for the sampling head.
Interconnections
to the sampling head circuits are provided
by the connector in the sampling head compartment of the
7S11.
The
7S11 and a 7Tll Sampling Sweep Unit operated in
the center plug-in compartments
of a 7000-Series
oscilloscope provide a single channel sampling system.
Two
7S11's and one 7Tll provide dual-trace sampling, using the
electronic switching in the oscilloscope vertical amplifier.
X-Y operation is provided by two 7S11's operated in the
center plug-in compartments
of the oscilloscope.
If a trigger pickoff is provided in the sampling head,
interconnections between
two 7S11's and the 7Tll
through the fixed and movable shoes provide a trigger
selection
circuit to trigger the 7Tl1. An internally
reconstructed signal
is provided to trigger a real-time
time-base
such as the 7850.
Sampled signals are presented to both the oscilloscope
vertical
amplifier and to the front panel connectors for
external use with auxiliary equipment such as pen
recorders.
Characteristic
Deflection Factor
Units/Division
Range
®I
TABLE 1-1
ELECTRICAL
Performance
2
to 200 in seven steps in 1, 2, 5
sequence. The Units/Division are
those labeled on the sampling head.
TABLE 1-1 (cont)
Characteristic Performance
Gain Accuracy
Within 3%
when
NORMAL/
(Ratio to add SMOOTH function
is I\IORMAL,
to accuracies of
with GAl N adjusted at any Units/
source, oscillo- Division switch setting.
Within 6%
scope, attenu- when NORMAL/SMOOTH
func-
ators, etc.)
tion is SMOOTH.
Units/Division Extends deflection
factor from
1
Variable Range
unit/division or less to at least 400
units/division.
GAIN Range
Permits adjustment of deflection
factor at any Units/Division switch
setti
ng for all 7000-series oscillo-
scopes.
DELAY Range
At least 10 ns.
Memory Slash
0.1 division or less at 20 Hz for
ambient temperature of O°C to less
than 30°C.
DC OFFSET
+1 volt to -1 volt or more.1
Range
OFFSET OUT
Range +10 volts
to -10 volts or more.
Relation
to
Actual Offset = (0.1) (Offset Out)
actual Offset
within 2%.
Source resistance 10 kn within 1%.
(related to
actual Offset)
VERTical SIGnal
OUT
Amplitude in (Signal input in volts) (U 2?0 /0' )
volts
nits IV
within 2%. 2.4 volts peak-to-peak
( Referenced maximum.
to input)
Deflection factor
200 mV/displayed division within
(Referenced
3% in +UP or INVERT.
to CRT)
Source resistance 10
kn within 0.5%.
1Unless otherwise stated on sampling head front-panel.
1-1
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Specification-7S11
ENVIRONMENTAL CHARACTERISTICS
Storage-altitude up to 50,000 feet or 15,000 meters and
-55°C. Operating characteristics are the same as those
listed in
the 7000-series oscilloscope manual.
PHYSICAL CHARACTERISTICS
Dimensions
Height 5 inches (12.7 centimeters)
Width 3 inches (7.6 centimeters)
Length 14
1/2 inches (37 centimeters)
Approximate dimensions including knobs and connec-
tors.
1-2
Finish
Weight
Net
Shipping
Front panel is anodized aluminum.
About 2 pounds (0.9 kilogram).
About 3 1/4 pounds (1.46 kilo-
grams).
STANDARD ACCESSORIES
Standard accessories supplied with the 7S 11 are listed on
the last
page of the Mechanical Parts List section. For
optional accessories available for use with this instrument,
see the Tektronix, I nco catalog.
®
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7S11
SECTION 2
OPERA
TING INSTRUCTIONS
Change information, if any, affecting this section will be found at the rear of the manual.
General Information
This section discusses installation, first time ope ration,
function of
front panel controls and connecto rs, basic oper·
ation and applications of
the 7S 11 . If you are unfam ili ar
with samp
li ng, it may be helpful to read Section 3, Basic
Tektronix Sampli
ng Principles, before proceeding with this
section.
T
he 75 11 is a single·channel sampling unit for use in a
sampling system
co nsisting of a Tektronix 7704 or 7504
Oscilloscope mainframe, a sampling sweep unit
(7 Tl1 ) or
real-time time·base and a 7S 11 ·sampling head combination.
The 7511 accepts an S-series sampling head which
deter -
mines the input characte
ri stics of the sampling system and
(except for
the Type 5-3 Sampling Head) provides a trigger
pickoff.
Th e 751 1 can be used for real ti me o per ation with real·
time time·base units such
as the 7 67 1 or 7B70 with the
7704 Oscilloscope, or the 765 1 or 7B50 with the 7504
Oscilloscope. An internal trigger source from
the display
signal
is provided for real time operation. Nevertheless, the
maximum useable sweep rate
is about .1 ms/div (with a 1
kH z signal ), since at higher frequencies the horizontal dot
size increases and the number of dots per division becomes
less than three.
The vertical deflection factors
of 2 to 200 are calibrated
to the units l abe led on the sampling head. Th ree-foot and
six·foot sampling head
extender cables are available to
op erate the S-series sampling heads remotely. Order th e
three-foot sampli
ng head extender cable by Tektronix P art
No. 012-0124· 00 . Order the six·foot sa mpling he ad ex-
tender cable by T
ektronix Part No. 012·0125 · 00 . Contact
your local Tekt ronix Fi eld Engineer or Representative for
price and availability
of these optional accessories.
In stalling the 7S11 in the Oscilloscope
Insert the 75 11 i nto the Right Vertical opening of the
oscilloscope and slide the 75 11 completely into the com·
par
tment . Th e 75 11 will lock into place with the spring
loaded latch knob.
Insert
the sampling head into the 75 11 with the latch
knob free to move until comp letely in the 751 1, then push
the latch to lock the head in place. To remove, pull the
latch knob away from the panel, then pu ll the unit from
the 75 11 .
The 7T11 Sampling Sweep Unit, normally used with the
75 11 , must be installed in the A Horizontal opening next to
the 7S
11 to make connections between the two units
through side
co nnectors (the movable and fixed shoes).
Mating
The 75 11 Vertical Output Amplifier gain must be
matched to th e osc ill osc ope CR T deflection factor for accu-
r
ate gain measurements. T he GAIN control, a screwdriver
adjustment
on the front panel, adjusts the Vertical Output
Amplifier gain of the 75 11 . Adjustment of th is GAIN con-
tr ol using the Type 284 Pulse Generator as a signal source is
shown unde r Equi va l ent Time Sampling Operation which
follows. For further Gain infor
mation, refer to the Gain
Adjus
tm ent instructions later in this section.
Fig. 2·1. Equ ivale nt time samp l ing system .
2-'
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Operating Instructions-7S11
FIRST-TIME OPERATION
Equivalent-Time Sampling Operation
Equivalent time sampling operation as described here is
provided by a system consisting of the 7504 Oscilloscope,
the
7S11 Sampling Unit, the Type S-1 Sampling Head, and
the 7T11 Sampling Sweep
Unit. The system is shown in
Fig. 2-1. Operation
of the oscilloscope, sampling head, and
the sampling
sweep unit is covered more fully in each in-
strument's manual. In this description, a Type 284
Pulse
Generator is used as a signal source.
Set the Oscilloscope Vertical Mode switch
to Right, the
A Trigger Source switch at Right Vert,
and the Horizontal
Mode switch
to A. Other oscilloscope controls may be in
any desired position.
Set the
7S11 controls as follows:
DELAY
+ UP/INVERT
DC OFFSET and FINE
VARIABLE
Units/Div
DOT RESPONSE
NORMAL/SMOOTH
Midrange
+ UP
Midrange
Pushed in
200
Midrange
NORMAL
Set the 7T11 controls as follows:
Time Position and Fine
Slope
Trig Level
Stability
Random/Sequential
Trig
Amp
Variable
Time/Div
Sweep Range
Int/Ext
Scan
Rep/Man/Ext Input
Fully clockwise
+
Midrange
Fully counterclockwise
Sequential
Xl0
Pushed in
.1 p.s
5 p.s
Int
Midrange
Rep
Type 284
Square
Wave Amplitude 1.0 V
Period 1
p.s
Mode Square Wave Output
Lead Time 75 ns
Connect the Square Wave Output signal of the Type 284
through a 5 ns coaxial cable (Tektronix Part No.
017-0512-00)
to the input connector of the Sampling Head
installed in the 7S11.
2-2
Center the trace on the graticule with the DC OFFSET
control and adjust the Trig Level and
Stability controls on
the 7Tll clockwise for a stable display. The GAl N adjust-
ment is properly set if the amplitude is 5 vertical divisions.
If the amplitude is not correct, adjust the GAl N control
with a small screwdriver for 5 divisions of vertical deflec-
tion.
NOTE
Operating the sampling head without the input con-
nector terminated
by a 50 n resistor or coaxial cable
will cause a few millivolts vertical shift to the zero
signal baseline.
This occurs because of the strobe
kickout signal is reflected from the open input con-
nector.
The kickout signal arrives back at the samp-
ling bridge during sampling time, while the bridge is
still conducting.
To avoid this baseline shift, connect
the input circuitry, then set the display zero reference
point.
Use at least 20 em of airline between the Type
S-1 input and a fast generator (such as a tunnel diode
pulse generator) or circuit that is sensitive to the fast
Strobe kickout
signal.
CONTROLS AND CONI\IECTORS
A brief description of the function and operation of the
controls and connectors
of the 7S11 follows. The control
setup chart, Fig. 2-2, shows the
front panel with an S-series
sampling head installed. This figure may be reproduced and
used as a test setup record for special applications or pro-
cedures,
or it may be used as a training aid for familiari-
zation
with this instrument.
DELAY (10 ns
RANGE)
+UP/INVERT
DC OFFSET ±1 V
Varies the
time position of the ap-
plied signal in relation to displayed
signals
from other vertical instru-
mEmts operating in the same main-
frame.
In the +
UP button setting, a posi-
tive
input signal deflects the CRT
beam upward. In the INVERT push
button setting, the displayed signal
is inverted, anegative signal deflects
the CRT
beam upward.
Applies internal signal offset volt-
age of +1 to -1 volt to the samp-
ling head. The input signal zero
reference (related
to the CRT) is
the DC Offset voltage instead of
ground. Permits all portions of a
+1-volt
input signal to be posi-
tioned through the CRT graticule
area vertically even at a deflection
factor
of 2 units per division. Verti-
®
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DATA:
Operating Instructions-7S11
TYPE 7511 SAMPLING UNIT SETUP CHART
FINE
DC OFFSET ± 1V
DELAY
(10n5 RANGE) 0 + UP
~ c:J'NVERT
VARIABLE (CAL IN)
©
GAIN
@
mVOLTS/DIV
TYPE S-1
SAMPLING HEAD
RISETIME
!S360ps
TEKTIIONIX®
60n
±6VMAX
NORMAL
OFFSET OUT
o
X10 lIIKO
VERTSIGOUT
o
.2V/DIV lIIKO
GND
o
SAMPLING UNIT
Fig. 2-2. Control Setup Chart.
2-3
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Operating Instructions-7S11
FINE
Units/Div
VARIABLE
(CAL IN)
DOT RESPONSE
cal deflection total is 16 mV with a
deflection factor
of 2 mV/Div, and
1.6 V when the deflection factor is
200 mV/Div. The front panel OFF-
SET jack allows accurate slide-back
voltage measurements
to be made
of part or all of a signal at lOX the
actual offset voltage applied
to the
head.
Provides vernier control
of the DC
Offset
function. Concentric with
the DC OFFSET ±1 V control.
Selects calibrated deflection factor
from 200 uriits/div to 2 units/div in
a 1-2-5 sequence. The units
are se-
lected and named on the adjacent
S-series sampling head. For ex-
ample,
with a Type S-l Sampling
Head, the
Units/Div switch set at
100,
each major division of deflec-
tion corresponds to 100 millivolts
of applied signal at the S-l input
connector when the VAR IABLE
control is at the (CAL IN) position.
Provides uncalibrated, variable ver-
tic a Ide flection factor between
Iabeled values
of the Units/Div
switch. When the
VARIABLE con-
trol is rotated from the counter-
clockwise position, displayed ampli-
tude varies
from less than 0.5 to
more than 2.5 times the calibrated
displayed amplitude.
Permits adjustment
of loop gain for
optimum dot transient response
when the NORMAL/SMOOTH
switch is in the NORMAL position.
GAl N Screwdriver adjustment permits cal-
ibration
of the vertical output am-
plifier gain to match the oscillo-
scope CRT deflection factor.
NORMAL/SMOOTH Selects unity loop gain at the NOR-
MAL push button setting. Reduces
the loop gain
to 0.3 or less at
SMOOTH push button setting.
NORMAL provides the correct loop
gain required when measuring rise-
time. SMOOTH reduces the effect
of random noise on the display
while requiring high sampling
dot
density for the correct displayed
risetime.
2-4
INT TRIG
OFFSET OUT
Xl0 10 kn
VERT SIG OUT
.2 V/DIV 10 kn
GND
Push button selects internal trigger
operation between
two 7S 11 's. I n-
ternal triggering is canceled when
associated
time base in the same
7000-series mainframe is switched
to external triggering. Lights up
when internal triggering is restored.
Unless otherwise specified on the
sampling
head front-panel, the open
circuit voltage atthis miniature con-
nector
is ten times the internal DC
Offset voltage as set by the DC
OFFSET control. The output resist-
ance
is 10 kn.
A facsimile signal (the same Mem-
ory output signal that drives the
Vertical
Amplifier) is available at
this miniature connector. The .2
V/D
IV label applies only when the
VARIABLE control is at its CAL
IN position and is limited to about
2.5 V maximum. (The
VARIABLE
control alters the CRT deflection
factor but does not change the sig-
nal amplitude fed to the VERT SIG
OUT miniature connector.) Output
voltage swing is not limited to the
magnitude displayed on the CRT.
Permits a non-sampling
type oscillo-
scope
to monitor the facsimile sig-
nal. Output resistance is 10 kn.
Miniature connector provides a con-
venient front-panel ground
point.
BASIC OPERATING INFORMATION
Dual Trace
The dual-trace features of the 7504 Oscilloscope Vertical
Mode permits observation
of two 7S11 displays simultane-
ously. This
is useful for comparing amplitude, risetime,
waveshape, and time relationship
of two signals. The sweep
can use either 7S11 as the internal trigger source. Be sure to
trigger from the 7S11 with the earliest signal event. Use
input signal cables with equal delays to preserve the time
relationship
of the two signals.
The
DELAY control adds a variable to the time coinci-
dence
of the two signals to accommodate sma" time differ-
ence in cables or sampling heads, so that both signals can be
displayed in the correct time relationship.
®
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Fig. 2·3. Dual trace operalion.
Dual·trace sampling operation requires two 75 11 Samp-
ling Unit s, a 7T11 Sampling Sweep Unit, and two S-series
sampl
ing heads installed in the 7504 Osc ill oscope. As wi th
single-trace operation,
the 7T ll must be installed in the A
Horiz open
in g adjacent to the 7511 for internal triggering
connections. The second 7511
is installed in the Left Vert
opening. See Fig. 2-3. Set
the controls as follows:
75
11 Sampling Units
DELAY
+
UP / IN VERT
DC OFFSET and FI NE
VAR I AB LE
Units/Div
DOT
RE SPONSE
NOR MA L/SMOOTH
Mid range
+ UP
Midrange
Pushed
in
50
Unity l oop gain
(
Fi g. 2-5)
NORMAL
7T11 Sampling Sweep Unit
Time Position and Fine
Slope
Trig Level and Stability
Random/Sequential
T
rig Amp
Variable
Time/
Div
Sweep Range
I
nt/Ext
Scan
Rep/Man/Ext In put
Fully clockwise
+
For triggered display
Random
Xl
Pushed
in
5 "'
50ps
Ext 50 n 2 V MAX
9 o'clock setting
Rep
Mode
Lead Time
Operating
In struction s- 7S 11
Type 284 Pul se Generator
Pulse
Output
75 ns
Set
the 7504 Oscilloscope Vertical Mode switch to
Chop. Connect the Type 284
Pu l se Output signal to the
sampl ing head input connectors through a power divider
and two 5 ns coaxial cabl
es. Connect the Type 264 Trigger
Output signal to the 7T 11 Trig Inp ut connector through a
50 n coaxial cable and 3 mm to 6NC adapter, supplied
with the
7Tll.
Ad just the 7T11 Trig L evel contro l for a stable display.
Center both tfaces on the graticu[e vertically with the
DC
OFFSET contro l s. This properly triggered dual-trace dis·
play
wi ll be sim il ar to Fig. 2·4A.
Time
Po sition. To show DELAY control operation,
change the 7T11 Sweep Range switch to 5
jJ.S and the
Time/Div switch 2 ns. Turn
the Time Position control
counterclockwise to place the rising portion
of the pulses
on the graticu
le . Time difference between the two displays
sho
ul d be eliminated by adjusting one or both DELAY con·
trois.
Add
The algebraic addition of two signals can be obtained
with
the Oscilloscope Ve rti cal Mode switch set in the Add
position. The DEL
AY control can be used to compensate
for small time differences between displays before making
accurate algebraic addition of the two signals. For accurate
algebraic addition, both sampl
in g heads should be same
type.
Use the same display as described under dual-trace
time positioning.
The two signals can be superimposed using the
DC OFF-
SE T and DE LA Y co ntr ols for most accurate time coinci·
dence setting. Set the Osc
ill oscope Vertical Mode switch to
Add. The superimposed signals
at dual-trace w ill be similar
to
the display of Fi g. 2·46.
Push the IN VERT switch on one 7S 11 . The display
shown
in Fig. 2- 4C is nearty a straight line indicating equal
and opposite signal amplitude. Rotate the DELAY control
of either 75
11 and notice that any time difference between
the two displays
will appear as a pulse, either positive or
negati
ve depending on the time position relative to the time
coinc
id ence.
Dot Response. The loop gain
of the samp li ng unit is
changed with adjustment of the DOT RESPONSE control
Random process sampling (available
wi th the 7 T1 1) 0
2·5
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Opera tin g Inst ru ction s- 7S11
multiple triggering (with a real-time time-base)
are conven-
ient ways
to ad j ust the DO T RESPONSE control to a set-
ti
ng of unity loop gain (each sample responding to the full
Fig_2-4. Di s plays of dual·trace iChopl and Add ope r ation.
2- 6
signal amplitude). 1 00 mi llivolts with the Type 284 Pulse
Ou
tput signal applied to two inputs through the power divi·
der (keeping the same signal connections as above) would
use
the Random mode of the 7 Tl1 .
Push
the +UP switch and the Osci ll oscope Vertical Mode
switch L
eft or Right button . Observe the display as the
DOT RESPONSE control is rotated clockwise and counter·
clockwise. A setting of uni ty loop gain occurs when the
random dots do not overshoot or undershoot the display.
see F
ig. 2·5.
F ig . 2 ·5 . loop gain ad just ment. trip le expos ure.
Vertical-Ho ri zo nt al (X - VI
Two 7S11 Sampling Units ope rated in the center com·
part ments (R i gh t Vert and A Horiz) of the 7504 Oscillo·
scope will produce
the X·Y display for phase difference
calcuiations. See Fig. 2-6A. Any time-related signals which
do not exceed sampling head input specifications may be
used
at the i nput connectors .
The 75 11 in the Right Vert compartment controls the
vertical
de fl ection and the 7S 11 in the A Horiz compart-
ment controls ho rizontal deflection. Set the Oscilloscope
Vertical Mode switch
at Right and the Horizontal Mode to
A Horiz. To produce a Lissajous figure, apply a sine wave to
both input connecto rs through the powe r divi der and 5 ns
coaxial cables. T he Type 284 1 ns Sine Wave Output can be
used. Set
the Units/Div switches at 10 and VAR IABLE
controls f
or a 6 division display both vertically and horizon·
tally;
the DELAY control of either 7S1 1 can be used to give
a circle display (900 out of phase) Of a diagonal straight line
(Do
or 1800 out of phase) for setting the 6 divisions. Set the
DELAY control for the diagon al straight line to eliminate
phase difference
at the 5 ns coaxial cab le inputs.
Afte r these adjustments. the system is ready to show
accurate phase difference displays over a wi
de range of fre·
quencies. Connect
the signals to the 5 ns coaxial cable in·
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puts. Fig. 2-6C shows a method for calculating the phase
difference between
the two signal s.
__ -, J I l~~!
L. __ -...J.... • .-.
~ ~ u .
.. . , ..
A. I nstalled Sampling Units .
C. Calcul a tion of e m.thod.
Fig. 2·6. X· Yoperation .
®!
Operati ng Instructions -7 S 11
Real Time Sampli ng
[ ~~~ J
Never operate the real-rime rime-base without the
side covers in place because of possible damage to the
movable shoe contacts
or to parts in the time-base
unit .
Real Time Sampling operation uses the three slowest
ranges
of the 7T1 1 Sweep Range switch or a real·time time·
base unit such as
the 78SO, 785 1, 7870 or 7B71 . The 751 1
provides oscillator controlled Strobe Drive pulses to the
sampling head, independent
of the real·time time·base unit.
The repetitive Strobe Drive pulses are turned on when the
7T1 1 Sweep Range switch
is at the 50,5, and .5 ms ranges
or when the time·base unit is a real-time time-base unit.
Real time internal triggering
is avai lable even when the
sampl
ing head does not contain a trigger pickoff circuit.
In stall the 7S11 and real·time time·base units in the center
compartments (or the Left Vert and B Hori
z) of the oscillo·
scope.
The 7504 Oscilloscope Calibrator
Output of 1 kHz,
Amplitude
sw itch at 0 .4 V into 50 n may be used as the
signal source. Connect the Calibrator
Output to the samp·
ling head input connector through a 50 n coaxial cable and
BNC to GR adapter. Set the Units/ Div switch to 100 and
the time·base unit Time/ Di v switch to .5 ms. Obtain a
stable display
wi th the Level/Slope control or the Trig
Level and Stability controls.
Real time sampling offers
DC offset capabilities matched
with good overload reco
ve ry. Random noise in the display
can be reduced through smoothing with the DOT
RE ·
SPONSE control and SMOOTH operation.
NOTE
Type 5·5 Sampling Head vertical noise may be reo
duced for real time sampling by lowering the asciI·
la t or frequen cy by adjusting Rep Rate control
(R415). Th is also wifJ lower the dot density.
Gain Adjustment
The GAIN contro l (a front·panel screwdriver adjust-
ment) matches the gain
of the 7S11 vertical output ampli·
fier to the Oscilloscope CRT deflection factor. The gain
should be checked and adjusted each time the 7S11
is used
wi th a different oscilloscope. A 1% difference is possible
between channels.
An accurate voltage source should be used into
the input
co nnector of the sampling head. The signal source imped-
ance
mu st be considered when it drives the input of a SO n
sampling head.
For
50 n input sampling head s, the Tektronix Typ e 284
(within 0.5%
at 10 ps and 1 pS), the 50 n Amplitude Cali ·
brator within 0.25%,
or a precision chopped voltage can be
2-7
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Operating Instructions-7S11
DELAY
+UP/INVERT
7S11
DC OFFSET and FINE
VARIABLE
Units/Div
DOT RESPONSE
NORMAL/SMOOTH
7T11
Time Position and Fine
Slope
Trig Level
Stability
Random/Sequential
Trig
Amp
Variable
Time/Div
Sweep Range
I nt/Ext
Scan
Rep/Man/Ext Input
Midrange
+UP
Midrange
Pushed in
200
Midrange
NORMAL
F ullyclockwise
+
Triggered display
Triggered display
Sequential
Xl
Pushed in
.2 J.ls
50J.ls
Ext
9 o'clock position
Rep
Type 284
Square
Wave Amplitude 1.0 V
Period 1
J.ls
Mode Square Wave Output
Lead Time Optional
used. The Oscilloscope Calibrator
output, with an accuracy
within 1 %, can be used also.
Using the Type 284. Set the controls
as follows using
the Type 284, accuracy withing 0.5% producing
7S11
deflection factor better than 3.5%, as the signal source to
check or adjust the GAIN control of the 7S11 and 50 n
sampling head:
Connect the Square
Wave Output signal from the Type
284
to the sampling head input connector through a coaxial
cable. Connect the Trigger
Output signal from the Type
284
to the 7Tl1 Trig Input connector through a coaxial
cable
and BNC to 3 mm adapter.
Adjust the
7Tll Trig Level control for a stable display.
Center the trace on the graticule
with the DC OFFSET
controls
and observe the square wave amplitude. If the
amplitude
is not 5 vertical divisions, adjust the GAIN con-
trol with a small screwdriver for 5 vertical divisions.
Using Oscilloscope Calibrator. Set the controls
as
follows using the Oscilloscope Calibrator as the signal
2-8
DELAY
+UP/INVERT
7S11
DC OFFSET and FINE
VARIABLE
Units/Div
DOT RESPONSE
NORMAL/SMOOTH
7T11
Time Position and Fine
Slope
Trig Level
Stability
Random/Sequential
Trig
Amp
Variable
Time/Div
Sweep Range
Int/Ext
Scan
Rep/Man/Ext Input
Calibrator Volts
Rate
7504
Midrange
+UP
Midrange
Pushed in
100
Unity loop gain
NORMAL
Fully clockwise
+
Triggered display
Triggered display
Sequential
Xl
Pushed in
.5ms
50ms
Int
Optional
Rep
4 V (0.4 V
into 50 n)
1 kHz
source
to check or adjust the GAil\! control of the 7S11
and 50 n sampling head. The 1 kHz, 0.4 V output has an
accuracy of ±1%, producing a 7S11 deflection factor
accuracy better than
4%.
Apply the signal from the Oscilloscope Calibrator Volts
output connector to the sampling head input connector
through a BNC coaxial cable
and BNC to GR adapter.
Adjust the Trig Level control for a stable display of the
square wave. Set the
DOT RESPONSE control to unity
loop gain (no overshoot or undershoot at the leading front
corner).
Center the trace on the graticule
with the DC OFFSET
controls and observe the amplitude.
If the amplitude is not
4 vertical divisions, adjust the GAIN control with a small
screwdriver
for 4 vertical divisions.
Vertical Signal Output
A composite signal is available at the Vertical Signal Out-
put jack (VERT SIG OUT). This signal is taken after the
sampling process
and is a proportional representation of the
display signal rather than the
input signal itself. In real time
sampling, the
output signal voltage follows the rate of the
internal
real time oscillator. The open circuit voltage at the
jack
is 200 millivolts per division of display when the
VARIABLE control is pushed in. The output resistance is
®I
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10 k.Q. The signal is not affected by the Oscilloscope Verti-
cal Mode switch. The signal is changed by the Units/Div
switch, the DC OFFSET controls,
and the NORMAL/
SMOOTH switches. The INVERT switch does not invert
the signal.
Output voltage swing is limited to 2.5 volts peak
or about 6 divisions above
and below the graticule center
depending on the actual position. The Units/Div switch
is
active but the output voltage is always proportional to the
CRT display (0.2
V/Div) up to 12 divisions maximum peak
to peak. Since the signal at the Vertical Output jack is an
equivalent time signal, it is useful for pen recorder applica-
tions when the sampling
sweep unit external input is driven
by the recorder.
The OFFSET
OUT monitor jack permits accurate
measurement
of the DC voltage set by the DC OFFSET
controls. The
output voltage has a range of +10 to -10
volts. Unless otherwise specified on the sampling head front
panel, the monitor jack output voltage is ten times the
internal DC offset voltage. The
output resistance is 10 k.Q.
BASIC APPLICATIONS
Vertical Deflection Measurements
Vertical displacement of the trace on the CRT is directly
proportional
to the signal at the sampling head input con-
nector installed in the 7S11. The amount
of displacement
for a given signal can be selected with the Units/Div switch.
To provide sufficient deflection for best resolution, set the
Units/Div switch
so the display spans a large portion of the
graticule. Also, when measuring between points on the dis-
play,
be sure to measure consistently from either the
bottom, middle, or top of the trace. This prevents the
width of the trace from affecting the measurements.
To make a vertical deflection difference measurement
between
two points on the display, proceed as follows:
1. Note the vertical deflection, in graticule divisions,
between the
two points on the display. Make sure the
VARIABLE control is in the CAL position.
NOTE
The vertical deflection factor is determined by the
Units/Div switch and the value
of the units of
measure as stated on the sampling head front panel.
The ratio of the input signal to the resultant deflec-
tion is called the deflection factor. For example, with
the sampling head unit values stated as mV/Div, and
the Units/Div switch set
to 20, the vertical deflection
factor
will be 20 mV/division.
2. Multiply the divisions of vertical deflection by the
deflection factor, and the external attenuator
or probe
®
Operating I nstructions-7S 11
attenuation factor (if any). The product is the voltage
difference between the
two points measured.
For example, suppose you measure 4.4 divisions of de-
flection between two points on the display and the Units/
Div switch is set for 20 mV /Div. Multiply 20 millivolts/
division by 4.4 divisions, the product is 88 millivolts. This is
the voltage difference at the input connector between the
two points on the display. Now assume there is a 10X
external attenuator (probe) between the
input connector
and the signal source.
To determine the actual signal voltage
at the source,
multiply 10 (the attenuation factor of the
probe)
by 88 millivolts; this product (880 mi"ivolts or 0.88
volts)
is the actual voltage at the signal source.
It is also possible to measure an instantaneous (or DC)
voltage
to ground from the display. This measurement is
accomplished in the same manner, except that with no sig-
nal applied, you must first establish a ground-reference
point on the CRT.
NOTE
To establish the ground reference point be sure the
input connector is either terminated by a 50.Q resis-
tor or coaxialcable connected to the input.
To do this, trigger the sampling sweep unit with the
signal source
and display a trace. Then, position the trace so
it is exactly aligned with one of the graticule lines. The
actual graticule line you select
will be largely determined by
the polarity and amplitude of the applied signal. After
establishing the ground reference, make no further adjust-
ments
with the DC OFFSET control.
Apply the signal and measure the voltage in the manner
previously described. Make all measurements 'from the
established ground reference
point. Accuracy of this meas-
urement is within ±3%.
If the applied signal has a relatively high DC level, the
ground-reference
point and the actual signal may be so far
apart
that neither will appear on the CRT. In this case, refer
to the following discussion on "Voltage Measurements
Using the DC Offset
Control."
Voltage Measurements Using the DC OFFSET
Control. Unless otherwise stated on the sampling
head
front panel, the DC offset voltage cancels the effect of an
applied DC voltage of up to ±1 volt at the sampling head
input. Also, accurate slideback amplitude measurements of
the applied signal can be obtained by positioning the dis-
play at various points and measuring the amount
of voltage
change at the OFFSET
OUT monitor jack.
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