Tektronix 7S11 User manual

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Tektro
7S11
SAMPLING
UNIT
" Tektro n i x ,
Inc .
Ρ . Ο . Box 500
B eaverto n , Orego n 97077

Serial Nu mber
1X @
COMMITTED TO E XCELLE NC E
PL E AS E C HE C K F O R C H A N G E I NF O RM ATIO N
AT THE R E A R O F T H IS M A N U A L .
INSTRUCTION MANUAL
F irst P ri n ting F EB 1970
070-0985-00

R evised JU N 1981

Co p yrig
h t ' 1970
Te k tro n ix, I n c . All rig
h ts
reser v e d .
Conte n
ts of this p
u blication may
n ot be reproduced
in
anyform without
t h e written
permission of Te
k tronix, Inc .
Products
of Te k
tronix, Inc . and
its s ub sidiaries
are
covered by U .S
. and foreig
n patents a
n d'or p e n ding
pate n ts .
TEKTRONIX,
ΤΕΚ , SCO PE -
M O B IL E , and

are
registere d
trademar k s of
Tektronix,
Inc . T ELE Q U
IP-
ΜΕΝΤ
is α registere
d trademar k
of Tektronix U .K
L imite d .
P rinte d in
U .S .Α.
Specification
and p rice c
h
a
nge
p ri v ileges
are reser ved
.

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
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 3-7
Display Sensitivity-Deflection Factor 3-7
DC Offset 3-7
Real-Time Sampling 3-8
Sweep Rates 3-8
SECTION 4 CIRCUIT DESCRIPTION
Introduction 4-1
Block Diagram 4-1
Feedback Loop and Pulse Amplifier Chain 4-1
Vertical Output Amplifier 4-1

S E CTIO N
S E CTIO N
REV . Β , JUL Y, 1977
TA BLE O F CO
N T EN TS (cont)
Swee p U nit Drive 4-1
R
ea d
out L ogic 4-3
Circuit
Descri p tion 4-3
Trigger L ogic
4-3
P ost Am p lifier and Attenuators
4-3
M emory
4-5
Out p ut Am p lifier
4-8
R eal Time Oscillator
4-8
Gate Generator
4-9
R ea d out L ogic
4-11
P ower Distribution and Decou p ling
4-11
5 M AI NT ENAN CE
Introduction
5-1
P reventive M aintenance 5-1
General
5-1
Cleaning
5-1
L ubrication
5-1
V isual Inspection
5-1
Calibration
5-1
P arts I d entification
5-1
P arts R e p
lacement 5-2
Troublesh
ooting 5-4
Intro duction 5-4
Troubles
hooting Ai d s 5-4
Troubles hooting
Tec h ni q ues 5-5
Transistor
C heck s 5-5
Diode
C h eck s 5-5
F
iel dE
ffect Transistors (FE T) 5-6
R ep ac k aging for Sh i p ment
5-7
6
PERF O RM A N C E CHE C K /CA L I BR ATIO N
Introduction 6-1
Test E q ui p ment R eq uire d
6-1
S h ort F orm P roce d ure 6-2
P reliminary P roce d ure 6-3
C heck -12 .2-
V
olt
P owerSu p p ly 6-5
C heck Inter d ot
B lan k ing 6-6
C heck
Dot R es ponse and Smoot h ing 6-7
A
d j ust M emory Gate W i d t h (13460) and
M emory Gain (C275) W it h N ormalizer
H
ead
6-7

SECTION 7

ELECTRICAL PARTS LIST
Abbreviations and
Symbols
Parts Ordering
Information
Index of Electrical
Parts List
Electrical Parts List
SECTION 8

DIAGRAMS
AND MECHANICAL PARTS
ILLUSTRATIONS
Diagrams
Mechanical Parts
Illustrations
Repackaging
Instructions
SECTION 9

MECHANICAL PARTS
LIST
Mechanical Parts
List Information
Index of Mechanical
Parts Illustrations
Mechanical Parts
List
Accessories
CHANGE
INFORMATION
Abbreviations and
symbols used in this manual
are based on or
taken directly 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 .
TABLE
OF
CONTENTS (cont)
Adjust Memory Gate Width
(R460) and
Memory Gain (C275)
With Sampling Head 6-8
Adjust Variable Balance
(13305) and
Smoothing Balance
(13245)
6-9
Check Deflection
Factor Accuracies,
Variable
Control Range and Adjust GAIN
6-10
Check Memory
Overdrive Recovery
6-11
Check Vertical
Signal Out
6-11
Check Vertical Gain
Change in SMOOTH
6-11
Check Memory Slash
6-11
Check
Delay
6-12
Check/Adjust Real Time
Sampling (13415)
6-12
Check DC Offset and Adjust
Position (13325)
6-12
Check Real-Time Trigger
Amplifier Output
6-14

Fig . 1-1 . 7511
Sampling Unit .

General Information
T he 7511
Sampling U nit is α single chan
nel vertical
amplifier p lug-in
un it d esigne d for op eration
i n Te k t r o n ix
7000-Series
Oscillosco p es . T h e 7511 accepts t
h e S-Series
Sam p li n g
H
eads .
T he Sam p li n gH ea d d ete
r mi n es the i n put
cha
r acte r istics a nd t he availability of α t
r
igge r
pic k off .
T h e S-Se r ies Sa mp li ng H
ea d used
can be
pl ugged i nto the
7511 or used remotely
on an op tio n al exte nde r ca b le un it .
T he 7511 pr ovi d es
t h ep ower fo r t h e sampli ng h ea d .
Interco nn ections to the
sampli n g h ea d circuits are p rovi d e d
b y t h e connector in t
he sampling h ea d com p artme n t of t h e
7511 .
T he 7511 and α

7T11
Sampling Sweep U nit ope r ate d in
t he ce n ter p
l u g-in compartme n ts of α 7000-Series
oscilloscope pr ovi d eα si n gle chann
el sam p li n g system . Two
7S1 1's
and one

7T11 p r ovi d e d ual-t r ace sampli n g, using t
he
electro n ic switc h ing i n t he oscilloscope vertical am
p lifier .
Χ - Υ op eratio n is pr ovi de d by two 7S1 1's ope r ate
d in t h e
center p lug-i n compa r tme n ts of the
oscillosco p e .
If α trigger pic k off is p r ovided in t h e
sampli n g h ea d ,
i n terco n n ections b etween two 7S11's an d
t
he Μ
1
t h ro ug h t he fixe dan d mova b le s h oes p rovi d eα
trigge r
selectio
n ci r cuit to t r igger the 7 Τ 11 . An
i n ter n ally
reconstructed sig n al is pr ovided to tr igge
r α r eal-time
time-base such as t h e 71350 .
Sample d signals are p rese
n te d to bot h t he oscilloscope
ve r tical am p lifier and
to t he front pan el co n necto rs for
exte rn al use wit
h auxiliary eq uipment suc h as pen
recor d ers .
C h
aracteristic
Deflectio nF acto
r
U nits/Divisio
n
R ange
SECTION
l
7S11
S PE CI
F I CA
ΤΙΟΝ
Ch a n ge i n fo r matio n , if a n y,
affecti ng t h is section will be fo un d at t
h e r
ea
r of t he ma nu al .
TA BLE
1-1
ELE
CT R ICA L
P erformance
2 to
200 i n seve n steps
i n 1, 2, 5
se q uen
ce . T he Un
its/Division a r e
those
labele d on t
he sam p li ng h ea d .
TA
BLE 1-1 (co n
t)
7511
' Un less ot h erwise stated
on samp ling hea d f r o n t- p a n el .
C h
aracte r istic Performan ce
Gain Accuracy
W it h i n 3% w h en
N O RM A L /
( R atio to
a dd S M OOT
H f u nctio n is N O RM A L,
to
acc ur acies of
with GAI N a dj usted at any U nits/
source, oscillo- Division
switc h setting . W it h i n 6%
sco p e, attenu-
w h en N O RM A L /S M OOT H fu n c-
ators, etc .)
tio n is S M OOTH .
Un its/Divisio
n E xte nds d eflection facto
r
f r om 1
Va r iable R an ge
unit/ d ivision or less to at least 400
u nits/ d ivision .
GAI N
Ra
n
ge
Permits ad j ustment of
d eflectio n
factor at any Un
its/Division switc h
setting
for
all
7000-se r ies oscillo-
sco p es .
D EL AY R
ange
At least
10 ns .
M
emo r y Slas h0
.1 division or less at
20
Hz
for
ambient te m peratu r e of 0 °
C
to
less
t h an 30 ° C .
DC
O
FF
S
E T +1 volt to -1 volt or
more .'
R an ge
O FF SE TOU T
R an ge +10
volts to -10 volts o r more .
R elatio n to Actual
Offset = (0 .1) (Offset Out)
actual Offset wit
h in 2% .
Sou r ce r esista n ce 10
k Ω with i n 1% .
( r elate d to
actual Offset)
VER Tical SIGnal
OU T
200
Amplitu d e i n
(Sig n al i n p u t i n volts)
Un its/D ιν
volts
wit h in 2% . 2 .4
volts
pea
k -to-pea k
( R efere n ce d
maximum
.
to i np ut)
Deflectio n
facto r 200 m V / d is p laye
d d ivisio n with i n
( R efere
nced 3% i n + UP or
I NVER T .
to C
R T)
So ur ce
resistance 10 k Ω wit h i n0
.5%
.

Dimensions
Height
Width
Length
5 inches (12 .7 centimeters)
3 inches (7 .6 centimeters)
14 1/2 inches (37 centimeters)
Approximate dimensions including knobs and connec-
tors .
STANDARD ACCESSORIES
Standard accessories supplied
with the 7511 are listed on
the last page of the Mechanical
Parts List section . For
optional accessories available
for use with this instrument,
see the Tektronix,
Inc . catalog .
Specification-7511
ENVIRONMENTAL
CHARACTERISTICS Finish
Front panel is anodized aluminum .
Storage-altitude up to 50,000 feet or 15,000 meters
and
Weight
-55 ° C . Operating characteristics are the
same as those
Net About 2 pounds
(0 .9
kilogram)
.
listed in the 7000-series oscilloscope manual .
Shipping About 3 1/4 pounds (1 .46 kilo-
PHYSICAL CHARACTERISTICS
grams) .

Ge n eral Information
T h is section d iscusses
installation, first time o p eration,
functio n of front p a n el controls a nd
con n ectors, basic o p er-
ation a nd a pp lications of t
h
e 7511 .
If
you
are unfa m iliar
with sam p ling, it may be
h
el
p
f u
l
to rea
d Section 3, Basic
Tektronix Samp li n g
P
ri
n ci p
les,
before procee d i n g wit h t his
sectio n .
The 7511 is α single-channel sam p ling u nit for
use in α
sa mp ling
system co n sisting of α Tektronix 7704 or 7504
Oscillosco p e
mai n frame, α sam p ling s w ee pun it (7T11) or
real-time time-base
an d α 7511-sa m pling hea d combination
.
T h e 7511
acce p ts
an
S-series sa mp ling h ea d w hich d eter-
mines t
h e inp u t c h aracteristics of the sa mp ling syste
m an d
(exce p t for the Type S-3 Samp ling H ea d
)
p rovi d es
α trigger
p
ic k off
.
T h e 7511
can be use d for real time o p
eration wit h real-
ti m e
time- b ase units s u c h as t h e 713711
or 71370 with the
7704 Oscillosco p e, or the 713511
or 71350 with t h e 7504
Oscillosco p e . An inter
n al trigger source fro m t he d is p la y
signal is pro v ide d
for real time o p eration . N evertheless, t
h
e
maxim u m useable
swee p rate is about .1 ms/ d iv ( w it
hα 1
kHz sig n al),
since at h igher fre q uencies t h eh
orizontal d ot
size increases an d t he number of dots p er
d ivision beco m es
less t h an
t h ree .
T h e vertical d
eflection factors of 2 to 200 a r e calibrate d
to t h e un its
labeled on the sa mp li n g hea d . Three-foot a n d
six-foot sa mp
ling hea d e x te nd er cables are available to
operate t h e S-series
sa mp ling hea d s re m otely . Order the
t h ree-foot sa mp ling
h
ea d
exte nd er cable by Te k tro n ix P art
No . 012-0124-00 . Order
the six-foot sa mp ling h ea d ex-
te nd er cable b y Te k
tro n ix P art
No
. 012-0125-00 . Co n tact
yo u r local Te k tronix F
iel d En gi n eer or Re p resentative
for
p rice and a
v ailabilit y of t h ese optio n al accessories .
I n stalli n g t h e 7511 i n t h e Oscillosco p e
Insert t h e
7511 i n to the Right V ertical o p e n ing of t h e
oscillosco p
e
an
d sli d e t h e 7511 co mp letel y i nto t h e co m -
part m
en
t
.
T h
e
7511
will lock into
place
with t h e s p ri n g
loa
d ed latc hk nob .
Α
SECTION 2
OPERATING
INSTRUCTIONS
Ch ange i n for
m atio n , if an y , affecting t h is section will be
fou nd
at t
h e rear of t h e manual .
Insert the sam
p ling hea d into the 7511 with t he latch
k n ob free to mo v e until
co mp
letely in the 7511,
then pu s
h
t he latc hto loc k t h e h ea d in p lace . To remove, pull the
latc hk nobaway from the p
anel,
then pull
the unit from
t h e 7511 .
The

7T11 Sa mp ling Swee p U nit, no r mally use
d wit h t h e
7511, must be i n stalle d in the Α H orizontal o p e n ing next to
the 7511 to make con n ections between the two units
t h rough si d e connectors (the movable an d fixe d shoes) .
M ati n g
7511
T he 7511 V ertical Out
p
ut
A mp lifier gai n must be
matc h e d to the oscillosco p
e CRT d eflection factor for accu-
rate gain
measureme n ts . T h e GAIN control, α screw d river
a d j u
stment on t h e front p anel, a d justs the V ertical Out p ut
A mp lifier gain of the 7511 . A d justme n t of this GAI N co n -
trol usi ng the Ty p e 284 P ulse Generator as α sig n al source is
s h o w nu n d er E q uivalent Time Samp ling O p eration wh ich
follows
.
F
or further
Gain information, refer to the Gain
A d j u st m e n t instructions later in t h is section .
Fig . 2-1 . Equ i v ale n t ti m e sa m pling system .

Ope r ating Inst r uctions-7Sl1
Equivalent-Time Sam p li n g O p eration
Eq uivale nt time sam p ling ope r atio n as d esc r ibe d he r e is
p rovide d by α system con sisti n g of t he 7504 Oscilloscope,
t h e 7511 Sampling U nit, t h e Ty pe S-1 Sam p ling H ea d , a nd
t h e 7 Τ 11 Sam p ling Swee p Un it . T h e system is s h own i n
F ig . 2-1 .
O p
eration of t h e oscillosco p e, sam p ling h ea d , a n d
t h e sam p ling sweep u n it is covered more fully in eac h in-
strumen t's manual . In t h is desc r i p tion, α Type 284 P ulse
Generator is used as α sig n al source .
Set t h e Oscillosco pe V ertical M o de switc h to R ig h t, t h e
Α Trigger So u rce switc h at R ig h t V e r t, a n d t h eH orizo n tal
M
o d e switc h to Α . Ot h e
r
oscilloscope controls may be in
any desire d positio n .
2-2
FIRST-TIME O PER ATIO N
Set t h e 7511 cont r ols as follows :
D EL AY M i d range
+
UP /I NVERT

+
UP
DC O FF S E T a nd F I NE

M i d range
V A RIA BLE

P us h e d in
U nits/Div

200
DOT RE S P O NSE

M i d ra n ge
N O RM A L /S M OOT H N O RM A L
Set t h e

7T11 co n trols as follows :
Time P osition an d F ine
Slope
T r ig L evel
Sta b ility
R an dom/Se q uential
Trig Amp
V ariable
Time/Div
Swee p Range
1 n t/ E xt
Sca n
R ep / Μαη /E xt I nput
Type 284
Square W ave Am p litu d e
P e r io d
M o d e
Lead Time
F ully cloc k wise
M i d ra n ge
Fu lly countercloc k wise
Se q ue n tial
Χ 10
Pus h ed in
.1 As
5 μ s
Int
Midrange
R ep
1 .0 V
1 As
S qua r e W ave Out
pu t
75
n
s
Co nn ect the S qu are W ave O u t put sig n al of the Type 284
t h roug h α 5 ns coaxial ca b le (Te k tro n ix Part No .
017-0512-00) to t h e i n put connector of t h e Sam p
ling H
ea
d
i nstalled in the 7511 .
Center t h e trace on t h e g r atic u le with t h e DC O FF SE T
control and a dju
st t h e Trig L evel an d
Stab
ility cont r ols
on
t h e 7 Τ 11 cloc k wise fo r α stable d isplay . T h e GAI N ad j ust-
ment is p ro p erly set if t h e am p litu d e is 5 vertical d ivisions .
If the am p litude is not correct, a d j ust t h e GAI N control
wit h α small screwd river for 5 divisio n s of vertical d eflec-
tion .
ΝΟΤΕ
Operating t he sampling h ea d wit hout t h e i nput con-
nector terminated by α 50 Ω resistor or coaxial cable
will cause α few millivolts vertical s h ift to t he zero
signal b aseline . T h is occu rs because of t he st r obe
k ic k o u t signal is reflected from t h e open input con-
nector . T h e kic kou t signal arr ives bac k at t h e samp-
ling bridge du ri ng sam p li ng time, w h ile t h e b r i d ge is
still conducting . To avoid t h is b aseline s h ift, connect
t h e inp u t ci rc u it r y, t h en set t h e d isplay zero r efer ence
poi n t U se at least 20 cm of airline between t h e Ty pe
S-1 i np ut a nd α fast gene rator (suc h as α tunnel d io d e
pulse ge ner ato r ) or ci r cuit t h at is sensitive to t h e fast
St r obe kic k ou t signal .
CO N T R O L S A N D CO NNE CTO R S
Α
brief d escri p tion of t h e fu n ctio nan do p eration of t h e
controls
and connectors of t h e 7511 follows . T h e control
setu pc h
art,
F
ig . 2-2, s h ows t h e front p anel withan S-series
sampli n g h
ead installed . T h is figure may b e re p roduce d and
u se d as α test set up reco r
d for s p ecial a pplicatio n s or p ro-
ce d ures, o r it may be
used
as
α training ai d for familiari-
zatio nwit h t h is instrume n t .
DE L AY (10 n s

V aries the time positio n
of t
h
eαρ
R A N G E)

p lied sig n al in r elatio n
to dis p laye d
signals f r om ot h e r vertical
inst r u-
ments operating i n t
he same m ai n -
frame .
+
UP
/I NVER T

In t h e + UP button setti n g, α p osi-
tive i n put signal d eflects t h e C R T
beam upwar d . In t he I NVER T pu s h
b u tton setti n g, t he dis p layed sig n al
is inverted, α negative signal d eflects
t h eC R T beam up war d .
DC O FF S E T ±1 V

A p plies i n te r nal sig n al offset volt-
age of +1 to -1 volt to the sam
p -
li
nghea
d .
T h
e
in pu t sig n al ze r o
refe r e n ce (relate d to t h e C RT) is
t
h e DC Offset voltage instea d of
g r oun d .
P
ermits all
p
ortio
n s of α
+1-volt in p ut signal to be posi-
tio n ed throug h the C R T graticule
area vertically eve n at α deflection
facto r of 2 units p er
d ivisio n . V e r ti-
Ο

DATA :
ΤΥΡΕ 7511 SA
MPL I NG UN IT S E T UP C H A R T
D EL AY
(10 ησ R A
NG E
)
ρ + υΡ
α I NVERT
VA RIA BLE (CA
L
IN)
F I NE
DC O FF S E T ±1 V
T EK TR O N IX
SA
MPL I N G UN IT
ΙΝΤ
TR
IG
σ
Fig . 2-2 . Con trol Set up C h a r t .
O p e r ati n g Inst ructio
n s-7511

O p erating
Instructions-7511
cal d eflection total is 16 mV with α
deflection factor of 2 mV /Div, and
1 .6 V w h en t he d eflection factor is
200
m V /Div . T h e front p anel O FF-
S
ET j
ac
k allows accurate sli d e-bac k
voltage measureme n ts to be ma de
of
p art or
all
of α signal at 10 Χ t he
actual offset voltage a pp lie d to t he
h ea d .
F I NE

P rovides vernier control of t h e DC
Offset function . Concentric with
t he DC O FF S ET ±1 V control
.
U nits/Div

Selects calibrated deflection
factor
from 200 un its/ d
iv
to
2 units/ d iv in
α 1-2-5 se
q uence . T he units are se
lecte d an d name d on t he a d j acent
S-series sam p ling h ea d . F or ex-
am p le, with α Ty p e S-1 Sam p ling
H ea d , t h e U nits/Div switc h set at
100, eac h ma j or d ivision of d eflec-
tion corres p on d s to 100 millivolts
of a pp lie d signal at t he S-1 in p ut
connector w hen the V A R IA BLE
control is at t h e (CA L IN) p osition .
V A R IA BLE

P rovides uncalibrate d , variable
ver
(CA L IN)

tical d eflection factor between
labeled values of t h e Units/Div
switc h . Wh en the VARIABLE con-
trol is rotate d from t he counter-
cloc k wise p osition, d is p laye d ampli-
tude varies from less t h an 0 .5 to
more t han 2 .5 times the calibrate d
d is p laye d am p litude .
DOT RE SP ON SE

P ermits a d j ustment of loop gain for
op
timum d ot transient response
w hen the N
O RM A L /S M OOT H
switc h is i n t he N O RM A L p osition .
GAI N
Screw d r iver a d j ustment p ermits cal-
ibration of
t h
e
vertical output am-
p lifier gain to matc
h t he oscillo-
scope CRT d eflection factor
.
N O RM A L /S M OOT H Selects unity loop
gain at t h e N O R -
M A Lp us h button setting . Re d uces
t h
e
loop gain
to 0 .3 or less at
S M OOT
H p us h button setting .
N
O
RM A L p rovi d es t h e correct loop
gain
re q uired w h en measuring rise-
time . S M OOT H re d uces the effect
of ran d om noise on the d is p lay
w h ile re q uiring h ig h sam p li ng dot
-

d ensity for t he correct d is p laye d
risetime .
2- 4
ΙΝΤ TR IG

P us h button selects internal trigger
o p eration between two 7S11's . In-
ternal
triggering is cancele d w h en
associated time base in t he same
7000-series mainframe is
switc he d
to external triggeri ng . L ig
h
ts up
w hen internal triggering is
restored .
O FF S ET O
U T

U nless ot h erwise s p
ecified
on
t he
Χ
10 101<2

sam p ling
head fro n t-panel, t h e o p en
circuit voltage at t h is
miniature con-
n ector is ten times t he
internal DC
Offset voltage
as set by t he DC
O
FF
SE
T control . T he out p ut resist-
ance is 10 k Ω .
VER T SIG O UT

Α facsimile signal (t he same
M em-
.2 V /DI V 10 k Ω

ory outp ut signal t h at d
rives
t
he
V ertical Amplifier) is available at
t h is miniature connector .
T
h e .2
V /DI V label app lies only
w h en t he
V A RIA BLE control is at its CA L
IN p osition an d is limited to about
2
.5
V maximum . (T he V A R IA BLE
control alters t he C RT deflection
factor but does not ch ange t he sig-
nal am p litu d e fe d to t he VER T SIG
OU T miniature connector .) Out p ut
voltage swing is not limite d to t he
magnitu de d is p laye d on t h e C RT .
P ermits α non-sampling ty p e oscillo-
sco pe to mo n itor t
he facsimile
sig-
nal . Out p ut resistance is 10 k
Ω .
GND

M iniature connector
provi d es α
con-
venient front- p anel
ground
p
oint .
Dual Trace
B ASIC O PER ATI NG I NF O RM ATIO N
T h e dual-trace features of t he 7504 Oscillosco p e V ertical
M ode p ermits ob servation of two 7511 d isplays simultane-
ously . T h is is useful
for
com
p aring
am
p
litu d
e, risetime,
waves
h
a p e, an
d time relations
h
i p of
two
signals .
T he
sweep
can use
eit h
er
7511 as t he internal trigger source . Be sure to
trigger from t he 7511 with t he earliest signal event . U se
in p ut signal cables with e q ual d elays to p reserve t he time
relations h i p of t he two signals .
T h e D EL AY control a dd s α variable to the time coinci-
den ce of t he
two
signals to accommo d ate small time d iffer-
ence in cables or sam p ling h ea d s, so th at both signals can b e
d is p laye d in t h e correct time relations h i p .

F ig . 2-3 . D u al trace o p eratio n .
Dual-trace sam p li ng op eratio n re qu ires two
7511 Sam p -
ling U n its, α 7T11 Sa mp ling Swee p U nit, an d
two S-series
sam p ling hea d s i n stalle d i n t he 7504 Oscillosco pe . As with
single-trace
op eration, t h e

7T11 mu st be i n stalle d in t he Α
Horiz ope
n ing
a
d jace n t to t he 7511 for inter n al triggering
con
n
ections
. T h e secon d 7511 is installe d in t h e L eft Vert
o p
eni ng . See Fig . 2-3 . Set t h e con trols as follows :
D EL AY
+
UP /I N VER T
DC O FF S ET an d FINE
VA R IA BLE
U n its/Div
DOT R ESP O N S
E
N O
R MA L /S M OOT H
Time
P ositio n an d F i ne
Slo p
e
Trig L evel an d Stability
Random /Sequential
Trig A mp
Variable
Time/Div
Swee pR
ange
I
n t/
Ext
Scan
R
e p /
Μαη /E xtln p ut
7511 Sa mp li ng Un its
Mid range
+ UP
Midrange
Pu
s h e d in
50
Un ity loo p gai n
( F ig . 2-5)
NORM A L
7T11 Sam p li n g Swee p Un it
Full y cloc k wise
For triggere
d d is p lay
R a nd om
Χ 1
P u shed in
5 μ s
50 μ s
Ext 50 Ω 2
V
MAX
9 o'clock setting
R e p
A dd
Typ e 284 P u lse Ge n erator
M o d e
Lea d
Time

75 ns
O p erating I n str u ctio n s-7511
Pu lse O utput
Set the 7504
Oscillosco p e V ertical M ode s w itc
h to
Chop . Co nn ect th e
Ty p e 284 P ulse Out p ut signal to
th e
sa mp ling h ea d
i np ut con n ectors th roug h α p ower d ivi d
er
a nd two 5 ns
coaxial cables . Co n nect t he Ty pe 284 Trigger
O u t p ut sig n al to t
he 7T11 Trig I np ut connector t h ro ughα
50 Ω coaxial
cable a nd 3 mm to BNC adap ter, s up
plie d
w it h t he 7T1 1 .
Ad j u st the 7 Τ 11 Trig L
evel con trol for α stable dis p la y .
Center bot h traces on
t he graticule vertically with t he DC
O FF S ET con trols .
T h is p ro p erly t r iggere d du al-trace dis-
play will be
similar to Fig . 2-4 Α .
Time P ositio n .
To
s h ow D E L AY control
op eration,
c h a n ge t
he 7T11 Swee p R an ge switc
h
to
5μ s and t he
Ti m e/Di
v switc h 2 ns . Turn t h e
Time P osition control
countercloc k wise to place t h e rising
portion of t he p ulses
on t h e gratic u le . Time differe
n
ce
between t he two dis p lays
s hou l d be elimi n ate d by ad j
usting one or both D E L AY con-
trols .
T h e algebraic a dd
ition of two signals can be obtai
n e
d
wit h t h e Oscillosco pe
Vertical Mode s w itc h set i n t h e A dd
position . T he D EL
AY control can be use d to co mp ensate
for s m all time d
ifferences betwee n d is p lays before
ma k i n g
acc u rate algebraic
a dd ition of t he two signals . For
acc u rate
algebraic a dd ition,
both sam p ling h ea d s s h oul d
be same
ty p e . Use t he same
dis p lay as d escribe d und er d ual-trace
time positioning .
T he two signals can
be su p eri mp ose d using t he DC O
FF-
S E T an d D EL AY
controls for most accurate
time coi n ci-
d ence setting . Set
t he Oscillosco pe Vertical Mo de
switc h to
A dd . T h e su p eri
mp osed signals at d ual-trace will be
si m ilar
to t he d is p lay of Fig .
2-4 Β .
P us h t he
I NVER T s w itc h on one 7511
. Th e dis p lay
sh ow n i n Fig .
2-4C is nearly α straig h t line
in d icati n g e qu al
an d o pp osite
sig n al a mp litu de . Rotate t
he D E LAY con trol
of eit h er
7511 an d notice t h at any
time d ifference bet w een
t
he
two
dis p lays will a pp ear
as α p ulse, eit h er positive
or
negative d e p end ing on t
he ti m e positio n relative to t
he ti m e
coinci d ence .
Dot R es p onse . T h e loop gain
of t he sa m pling u n it is
c h an ge d with a d j ust m ent of
t he DOT R E S P O NS E control
.
R ando m p rocess sam p
ling (available wit h t h e 7 Τ 11)
or
2- 5

Operating
Instructions-7511
multiple triggering
(with α real-time time-base) are conven-
ient ways to adjust the
DOT RESPONSE control to α set
ting of unity loop gain (eac
h sam p le res pond ing to t he full
Α . Pr op e
r
du
al-t r ace triggering .
Β . Sup erim p ose d sig n als i n A dd mo de .
C . S u peri m pose d sig n als, r ig h t 751 .1
inve r ted i n A
dd m ode .
F ig . 2-4 . Displays of du al-t r ace (C h op) a n d A dd
operation .
2-6
signal am p litude) . 100 millivolts with the Type
284 Pulse
Out p ut signal app lied to two in p uts t h roug h t he p ower
divi-
der ( kee p ing t he same signal connections as above)
woul d
use t he R a nd ommo d e of
t he
7T1 1 .
Push t he
+
UP switc h and t he Oscillosco pe Vertical M ode
switc h L eft or
R
ig h t button . O b serve the d is p lay as t
he
DOT RE S P O NSE con tr ol is rotate d cloc k wise an d coun ter-
cloc k wise . Α setting of unity loop gain occurs w
h
en t
he
ran d om dots
d o not overs hoot or und ers hoot t he d is p lay,
see Fig . 2-5 .
_ . .
~ ...  . :_
: ._ . .
DOT RE S P O NS E
Cloc k wise
Loop Gain >1
r . .,
. . . , .

.
α
--

-
Un
it
Loop
Gai n
DOT
RE S PON SE
Counte r cloc k wise
Loop Gain < 1
F ig . 2-5 . L oop gain adjustment, triple exposure .
V ertical-Horizontal (X-Y)
Two 7511 Sam p ling U nits op erate d
in
the
center com-
p artments ( R ig h t Vert an d Α H oriz) of the
7504 Oscillo-
scope will p ro duce t he Χ -
Υ
d is p lay for ph ase
d ifference
calculations . See Fig . 2-6 Α . Any time-related
signals w h ic h
d o not excee d sam p ling h ea d in p ut s p ecifications
may
be
use d at t he input connectors .
T he 7511 in t he R ig h t Vert compartment controls t
he
vertical d eflection an d t he 7511 in t he Α H oriz
com
p art-
ment controls h orizontal deflection . Set the Oscillosco p
e
Vertical Mo d e switc h at R ig h t an d t h eH orizontal Mo
de to
Α H oriz . To p ro duce α L issa j ous figure, apply α sine
wave to
both in p ut co n nectors t h roug h t he power d
ivider
and 5
ns
coaxial cables . T h e Ty p e
284 1 ns Sine W ave Output can be
use d . Set t he Units/Div switc h es at 10 an d VA R IA BLE
controls for α 6 division dis p lay
both vertically an d h
orizo
n -
tally ; t h eD EL AY co n trol of eit h er 7511 can be use d to give
α circle dis p lay (90 ° out of ph ase) W α d iago n al straig h t line
(0
° or
180
°
out of ph ase) for setting t he 6 divisions . Set t he
D EL AY control for
t h e d iago n al straig h t line to eliminate
p h
ase d ifference at t h e 5 ns
coaxial cable i n p uts .
After
t
h
ese
a d j ustments, the system is rea d y to sh ow
accurate ph ase d ifference dis p lays over α wide range of fre-
q uencies . Connect t he signals to t h e 5 ns coaxial ca b le in-

p uts . F ig . 2-6C sh ows α m et h o d
for calculating t he p h ase
d ifference between the t w o signals .
F ig . 2-6 .
Χ
-
Υ operatio n
.
OA
1
R eal Ti m e Sam p ling
CAUTION
ΛλΜ r λΝλ '
Op erating I n str u ctions-7511
Never operate t
h e r
eal-ti m e ti m e-base wit hou t t h e
side cove r s in place because of possible da m age to t h e
movable s h oe contacts o r to p arts in t h e time-base
un it .
R eal Ti m e Sa mp li ng op
eratio n uses the t h ree slo w est
ra n ges of t he 7 Τ 11 Swee p
R ange switc h or α real-ti m e time-
base u nit suc h as t he 71350, 71351, 71370
or
71371 .
The 7511
p rovi d es oscillator con trolle d Strobe
Dri ve p ulses to t he
sa mp ling h ea d, in depende n t of t
he real-ti m e time-base u nit .
T h e re p etitive Strobe Drive p ulses
are turned on wh en t he
7T11 S w ee p
R ange switc h is at t h e 50, 5, and .5 ms ranges
or w hen t he ti m e-base un it is α real-ti m e ti m e-base u nit .
R eal ti m e inter n al triggering is available even w hen t he
sa mp ling h ea d does not contain α trigger p ic k off circuit .
I n stall t he 7511 and real-ti m e time-base units in t he center
co mp artments (or t h e L eft
V
ert an d
Β H oriz) of t he oscillo-
sco pe .
T
h e 7504
Oscillosco p e Calibrator Out p ut of 1 kHz,
Am p litu de
switc h at 0 .4 V into 50 Ω may be use d as t he
signal source . Co n nect t he Calibrato r Out p ut to t he sam p -
ling h ea d in p ut connector t h roug h α 50 Ω coaxial cable an d
BN C to GR ada p ter . Set t he U nits/Div switc h to 100 an
d
t he ti m e-base un it Time/Div switc h to .5
ms .
Obtain
α
stable dis p lay with t
he
L
evel/Slo
p e control or
t he Trig
L evel an d
Stability
controls .
R eal time sa mp ling offers DC offset ca p abilities matche d
wit h goo d overloa d recover y .
R
and om n oise i n t h e d is p lay
can be
re d uce d t h
ro
ugh
smoot
h ing
with t h e
DOT R E-
SP O N SE con trol and SM OOT H op eration .
Gai n
A
d j u
st m
e
nt
NO
ΤΕ
Type S-5 Sa m pli n g Head v ertical noise may be re-
d uced for real time sampling by loweri n g t he oscil-
lator
freq
u ency
by
ad
j
usting R ep R ate control
(8415) . Th is also will lower t he dot den sity .
T he GAI
N
control
( α front- p anel screwd river a d j ust-
ment) m atc h es t he gai
n
of
t h
e
7511 vertical out p ut ampli-
fier to t h e Oscillosco p e C
RT
d eflection factor
. T he gain
s h oul d be ch ec ked and ad j uste d eac
h
ti m e
t h
e
7511 is use d
w it h α different oscillosco p e . Α 1% ο d
ifference
is
p ossible
bet w een ch a n nels .
An acc u rate v oltage so u rce s h oul d be use d into t he i np ut
connector of t h e sa mp ling h ea d . T he signal so u rce imped -
ance m ust be con si d ere d w h en it d ri v es t h e i np ut of α 50 Ω
sa mp ling h ea d .
F or 50 Ω i np ut
sampling h
ea d s, t he Te k tronix Ty p e 284
( w it h in 0 .5% ο at 10 μ s and 1 μ
s),
t he 50 Ω Am p litu d e Cali-
brator wit h in 0 .25%, or α p recision ch o p pe d voltage can be
2- 7

2- 8
used . T he Oscilloscope
Calibrator out p ut, wit h an
accuracy
wit h i n 1%, can be u se
d also .
U sing
the Typ e 284 . Set t h e co
n trols as follows
using
t he Ty pe 284,
accu r acy wit h ing 0
.5% pr od ucing 7511
d eflectio nfactor bette
r t h an 3 .5%, as
t
he
signal sou r ce to
ch eckor a dju st t he
GAIN control of the
7511 a n d 50
Ω
sam
p ling h ea d :
Con nect
t he Sq ua r e W
ave Out put sig n al
from t he Ty pe
284 to the sam
p ling h ea d
in p ut connector t h roug
hα coaxial .
ca b le . Con
n ect the T r igger Output
signal from
the Ty p e
284 to the
7 Τ 11 T rig I n put
connector th roug
hα coaxial
ca b le and BN
C to 3 mm adapter
.
A d j ust the

7T11 T rig L evel
control for α sta b le dis p lay .
Center the
trace on the g r aticule
with t h e DCO FF SE
T
controls and
observe the s q uare
wave am p litude . If t
h e
amplitu de
is n ot 5 vertical
divisions, a dj ust t h e
GAI N
con-
trol
with α small screwd r iver
for 5 vertical d ivisions .
U sing Oscilloscope Cali br ato
r . Set t h e cont r ols as
follows using t he Oscilloscope
Cali br ator as the signal
V ertical
Signal Output
sou r ce to checkor
a dju st t h e GAI N co n tr ol of t h e
7511
an
d 50 Ω sampli ng h ea d . T he 1 kH
z, 0 .4 V o u tput h as an
accuracy
of ±1%, pr od u cing α 7511 deflection factor
acc uracy bette
r t han 4% .
Apply t h e sig n al f r om the
Oscilloscope Calibrator V olts
out pu t co n nector to t
he sampling h ead i n put co nn ector
t hr oug h α BN C coaxial
ca b le and BN C to G R ada p ter .
Ad ju st t he T rig L evel co
n
trol
for α sta b le d isplay of the
s q ua r e wave . Set the
DOT RE S P O NS E co n tr ol to unity
loop gai n (no overs
h oot o r und ers h oot at t he leadi ng fro
n t
corne r ) .
Center the trace on the g r aticule
with the DCO FF SE T
co n trols and ob serve t h e am p litu d e .
If the am p litu de is n ot
4 vertical divisions, ad ju st the GAI
N
co nt r ol
with αsmall
screw d river for 4 vertical d ivisions .
Α com p
osite sig n al is availa b le at the
V ertical Sig n al Out-
put j ack
(VER T SIG OU T) . T h is
sig nal is ta ken after the
sam p li ng process
a nd is α pro p ortional
r epresentatio n of the
d is p lay signal
rathe r t han t h e i n put sig n al itself
.
In
real time
sam p li n g,
the out p ut signal voltage follows
the rate of the
inter n al real
time oscillator . T h e open
circuit voltage at t he
j ack is
200 millivolts p er d ivisio
nof d isplay w h en t h e
VA R IA BLE co n t r ol is pushed
in . T h e output resistance
is
Ο
71
7 Τ 11
7 Τ 11
Time
P ositio n and F i ne F ully clockwise
Time P ositio n an
dF i ne F ully clockwise
Slope
Slo p e
Trig L evel
Trigge r ed
d is p lay Trig L evel
T r igge
r ed d is p lay
Stability
Trigge r ed d
isplay Stab
ility
Triggere d dis p lay
R an d
om/Se que n tial Se q
uential
R
a
nd om/Se qu ential Se q
uential
Trig
Amp Χ 1
Trig Amp
Χ 1
V a r iable
P ushed in
Variable
P ushed in
Time/Div
.2 μ s
Time/Div
.5 ms
Swee p R ange
50μ s
SweepR ange
50 ms
Ι η t/ E xt
E xt
1 nt/ E xt
Int
Scan
9 o'clock p
ositio n
Scan O p
tional
R ep/ Μαη
/Extlnput R ep
Rep / Μαη /Extlnput
R ep
Type284 7504
S
quare W ave Amplitude
1 .0 V
Calibrator Volts
4 V (0 .4 V
P erio
d
M ode
1 As
Sq
uare W ave Out
p ut
into 50 92)
L ead Time
Op
tional
R ate
1 kH z
Ope
r ating I n structions-7511
7511
7511
D EL AY
M idra nge D
EL AY
M
i
d r ange
+
UP/INVERT
+ UP
+ UP/INVERT +UP
DC OFFSET and
F INE Midrange
DCOFFSET and FINE Midrange
V A R IA BLE
Pu s hed in
VA R IA BLE Pushed in
Un its/Div 200
Un
its/D ίν 100
DOT RE SP ON S
E M i d r ange
DOT RE S P ONS E U nity loop
gai n
N O RM A L/S M OOT
H NO RM A LN
O RM A L /S M OOT HNO
RM A L

10 k Ω . T he sig n al is not affecte dby the Oscillosco pe Verti-
cal M od e switc h . T he signal is ch ange dby t h eU nits/Div
switc h , t he DC O FF S E T controls, a nd t he N O
RM A L /
S
M
OOT
H
switc
h
es .
T
he
I NVER T
switc
hdoes not invert
t
h e signal .
Out p ut voltage
swing
is limite d to
2
.5
volts p ea k
or about
6
d ivisions above and below t he graticule center
dep e
nd ing on
t
he actual p osition . T
h e U
nits/Div switc h is
active but t h e output voltage is always p ro
p ortional to t he
C RT d is p lay
(0 .2
V /Div) up to 12 d ivisio n s maximum peak
to p ea k . Since t he signal at t he V ertical Out p ut j ack is an
eq uivalent time signal, it is useful for p en recor d er ap p lica-
tions w hen t h e sam p ling swee p unit external in p ut is d rive n
by the recor d er .
T he O FF S E T O UT monitor j ac kp ermits accurate
measurement of t he DC voltage set by t he DC O FF SE
T
controls . T h e out p ut voltage h as α range of +10 to -10
volts . U nless ot h erwise s p ecified on the sam p ling h ea d front
p anel, t he monitor j ac k out p ut voltage is ten times t
he
internal DC offset voltage . T he output resistance is 10 k Ω
.
B ASIC APPLICATIONS
V ertical Deflection Measurements
V ertical d isplacement of t he trace on t h e CR T is directly
p ro p ortional to t h e signal at t h e sam p ling h ea d input con-
nector installed in t h e 7511 . T he amou n t of dis p
lacement
for α given signal can be selecte d wit h t
he
U
nits/Div switc h .
To p rovi de sufficient d eflection
for
best
resolution, set t he
U nits/Div switc h so t
he
dis p lay s pans α
large portion of t he
graticule
.
Also, w h
e
n measuri n g
between
p oints on t he dis-
play, be sure to
measure consiste n tly from eit h er t he
b ottom, mi d dle, or to p of t h e trace . T h is p revents t he
wi dth of t he trace from affecti ng t he measurements .
To ma
ke α vertical d eflection d ifference measurement
between two p oints on t he d isplay, p roceed as follows :
1 . Note t he vertical deflection, in graticule d ivisions,
between the two p oints on t he d is p lay .
M
ak e s
u re t he
V A R IA BLE control is in t he CA Lp
osition
.
ΝΟΤΕ
Th e vertical deflection factor is determined by t he
U nits/Div switc hand t h e value of t he units of
measure as stated on t he sampli n gh ead front panel .
Th e ratio of t h e i n put signal to t he resultant deflec-
tion is called t h e deflection factor . F orexample, wit h
th e sampling h ead unit values stated as m V /Div, and
t h e U nits/Div switc h set to 20, t h e vertical deflection
factor will be 20 m V /division .
2 . M ulti p ly t h e divisions of vertical deflection by t h e
d eflectio n factor, an d t h e external atten u ator or p robe
Op erating Ι nstructio n s-7511
attenuation
factor (if any) . T he pro d uct is t he
voltage
d ifference
between t he two p oints measured .
F or exam p le, su pp ose you measure
4 .4 d ivisions of de-
flection between two p oints on t he d is p lay and
t he U nits/
Div switc h is set for 20 m V /Div .
M
ulti
p ly 20 millivolts/
divisio n by 4 .4 d ivisions, t h e p ro d uct is
88 millivolts . T h is is
t he voltage d iffere n ce at t he in
p
ut
connector between t he
two p oints on t h e d is p lay . Now assume
th ere is α10 Χ
external attenuator (probe)
between t h e in p ut connector
an d t h e signal source . To
d etermi ne t he actual sig n al voltage
at t h e source, multi
p ly 10 (t he attenuation factor of t he
p robe) by 88
millivolts ; th is p ro d uct (880 millivolts or 0 .88
volts) is t he
actual voltage at t he signal source .
It is also possible to measure an instantaneous (or
DC)
voltage to groun d from t he d is p lay .
T h
is
measurement is
accom p lis h ed in the same man
n
er, exce p t t h at
wit hno
sig-
nal a p p lie d , you must first establis hα
groun d -reference
p oint on t he C R T .
ΝΟΤΕ
To establis h th
e ground reference p oin t be sure t h e
input connector is eit her
terminated by α 50 Ω resis-
tor o r coaxial cable
connected to t he input .
To d o t h is, trigger t he sam p
ling
swee
p unit with t he
signal source an d d is p lay α trace . T h en, p osition t h e trace so
it is exactly aligne dwith one of t he graticule
lines . T he
actual graticule line you select will be largely d
etermine
dby
t h e p olarity an d am p litu de of t he a pp lied
signal . After
establis h ing t he ground reference, ma k e no furt
h
er
a d j ust-
ments wit h t h e DC O FF S E T control .
Appl y
t h e signal and measure the voltage in t he manner
p reviously d escribe d . M a k e all measurements from t h e
establis hed ground reference poi n t . Accuracy of t h is meas-
urement is with in ±3% .
If
t
he a
pp lied
signal
h as α relatively h ig h DC level, t he
ground-reference p oint an d t he actual signal may be so far
ap art th at neit h er will a p pear on t he CR T . In t h is case, refer
to t he followi ng d iscussion on " V oltage M easuremen ts
U sing t he DC Offset Control ."
V oltage M easu r ements U sing the
DC O FF S
E
T
Control . Un less
oth erwise stated on the sam p li ng h ea d
front p anel, t he DC
offset voltage cancels t h e effect of an
a pp lie d
DC voltage of up to ±1 volt at the sam p li n g h ea d
in p ut .
Also, accurate sli d ebac k amplitu de measureme n ts of
t he a pp lie d signal
can be obtaine dby p ositioning t h e dis-
play at various p oints
an
d
measuring t h e amount of voltage
change at t h e O FF S ET OU T
mo
n
itor j ac k .
2- 9

Operating Instructions-7511
Source resistance for the
voltage at the OFFSET
OUT
monitor j ack is 10 k
Ω ; therefore, meter loa d ing may
be α
factor if other
than an infinite-im ped ance
meter is use d .
The accuracy
of the DC offset voltage
measurement
depen d s on
the accuracy an d t he loa d ing effect
of the meas-
uring d
evice
.
The following measuring devices are
recom-
men d ed, in or d er of
p reference, for monitoring
voltage at
the OFFSET
j acks .
(1)
Differential, non-loading DC voltmeter
accurate within
0 .2% or
better . This type of d evice p rovi
d es absolute
offset voltage
measurements accurate within
2% . M eas
urements of
small changes in offset voltage
can be
ma de more
accurately than 2% .
(2) V acuum-tube
voltmeter with an in p ut im p edance
of at
least 10 megohms
. Accuracy of the V TVM s
hould be as
h igh as p ractical
.
(3) Zero-center
±1 mA milliammeter with as
h igh
an
accur-
acy as p
ractical . The milliammeter
shoul dbe connecte d
directly
between the OFFSET
OUT monitor j ack an d
ground
. When using α
milliammeter, 1 milliam p ere is
equivalent to 1 volt of
the actual offset voltage .
The
loa d ing effect is
within 2% ο + the error p ercentage d
eter-
mine d by : 100
(Rmeter/10000) .
Slideback
Measurement P rocedure . To measure
the volt-
age d ifference
between
two
p oints on α waveform
(such as
peak or p eak-to-peak
volts), procee d as follows :
1 . Set the DC OFFSET control to about midrange
.
2 . Apply t he signal
to be measure d to the sampling
h ea d
input . Adjust for
α stable d isplay with about
7d ivisions of
vertical
deflection between the two points of
the signal to
be
measured
.
3 . W ith t he DCOFFSET
controls, move one of the
p oints to be measured to the center
line of the graticule and
measure the voltage at the
OFFSET OUT monitor j ack . U se
one of the measuring d evices
mentione d p reviously .
4 . W ith t he DC
OFFSET control, move the dis p
lay so
the other p oint to
be measured is aligne dwith t he
center-
line of the graticule an d again
measure the voltage at the
OFFSET OUT monitor j ack .
5 .
Find the difference
between the voltage measured
in
ste p 3 an d t he voltage measure
d in ste p 4, an d divi de by 10 .
2- 1 0
The result is the
voltage d ifference, in volts, between the
two p oints on the
waveform . This voltage tolerance is ±2% ο
of the
input signal p lus the tolerance an d loa d ing effect of
the measuring d
evice .
U se of
Smoothing
R
and
om p rocess sam p ling does n ot generally
p ermit the
use of smoothing . This p rocess re q uires unity loop
gain to
construct α coherent d is p lay from the
samples taken at ran-
d om . When using ran d om p rocess sam
p ling, operate the
7511 with t he N
ORMAL switch pushed in, an d adjust the
DOT RESPONSE
control to unity
loop
gain .
Normal p rocess
sam p ling does p ermit the use of smooth-
ing . Time and
amplitu d e noise may sometimes be objection-
able when
operating at minimum d eflection factors or
max-
imum
sweep rates . F or Smoothing operate
the 7511 with
t
he SMOOTH switch p ushed in .
This
will reduce the ran d om noise by about
one h alf by
decreasing
the gain of the sampling fee dback loop .
F ig . 2-7
shows
the a d vantage of using smoothing when
observing α
low-amplitude signal .
Dot
Density . N ormally the risetime of the
d isplay will
not be
significantly affected in smoothe dop eration
if the
d ot density is
sufficient . If, h owever, the d isplay
waveform
shape is
affecte d w hen the SMOOTH switch is p ushed in, α
com p romise
must be ma de between smoothing an ddot
density .
F ig . 2-7C illustrates the effect p ro duced
when the
dot d ensity
is low with smoothe d o p eration .
This effect can
be com
p
ared to
the h igh d ot density of
the same in p ut
signal as
shown in F ig . 2-7 Β .
"False" Dis p lays
B ecause sam p ling d is p lays only
α fraction of any one
cycle of α repetitive signal,
it is sometimes p ossible to
obtain α false
equivalent-time dis p lay of the signal . The
incorrect equivalent-time d is p lay occurs
when the sampling
rate is an exact multi p le of the signal rate .
Each sample
vertical position represents the correct
signal am p litu d e, but
an incorrect number of samples is taken,
causing the false
e q uivalent-time d is p lay .
F alse equivalent-time
dis p lays
can
be d etected by chang-
ing the sampling sweep
unit
Scan
control ; i .e ., changing the
dot d ensity . Occasionally such α
false e q uivalent-time dis-
play occurs when t he
sampling sweep unit triggering circuit
is adjusted to free run,
and at the same time the triggering
signal am p
litu de synchronizes it falsely . Any time
the dis-
play
equivalent time changes when c hanging the dot
d en-
sity, alter the Time/Div switch to obtain α d
is p lay with an

eq uivalent time that d oes not change with dot d
ensity
change . U sually the swee p rate shoul d be
increase d (turn
the Time/Div control
clockwise),
but some
false displays
can be obtained when the signal repetition
rate is slower
than can be shown b y equivalent-time
normal process sam p -
Α .
Normal operation .
Β . S moothed
operation .
C . Smoothed operation, low dot density .
Fig . 2-7 . Use of
NORMAL/SMOOTH switch in sequential process
sampling for decreasing display noise when viewing α low amplitude
signal .
ling . When t hat occurs,
the d is p lay can usually be correcte d
b y changing to
real-time sam p ling . Fig . 2-8 gives an exam p le
of α false an d α
correct
d isplay
for two sweep rates when
the signal is α 500
MHz
sine
wave .
Time Domain R eflectometry (TDR)
T he 7511 with the Ty p e S-1 Sam p ling H ea d can be use d
for Time Domain R eflectometry d isplays . TDR using the
Type 284 Pulse Generator is d escribe d in the Type 284
Instruction Manual . Very fast d isplays, and special TDR
analysis of small reactances is p ossible with t he Type S-4
and the Type S-50 . See the Type 1S2 Instruction Manual
for information about such fast d isplays .
P en R ecor d er O p eration
Operati ng Instructions-7511
T he signal available at the V ert Sig Out j ack provides α
convenient source for d
riving the
Υ
axis of α p en recor d er .
It is
common practice to manually scan
the CRT (with t he
Α . F alse display .
Β .
Correct display .
Fig .
2-8 . Typical false and correct dis p lays using α 500 MHz signal
input .
2- 1 1