Tektronix 7S14 User manual

Tektmnlx, Ine.
P.O. Box 500
Beaverton, Oregon 97077
070-141 [Foe
Product Grwp 42
COMMlTTED M EXCELLENCE
PLEASE CHECK FOR CHANGE INFORMATION
AT f HE REAR OF THIS MANUAL.
DUAL TRACE
DELAYED SWEEP SAMPLER
INSTRUCTION
MANUAL
Seriaf Number

Copyright 1973 Tektronix, Inc. All rights reseN€d.
Contents of this publication may not b reproduced in any
form without the wr~ttenperrn~ssion of Tektronix, Im.
Products of Tektronix, Inc. and its subsidiariesare covered
by U.S. and foreign patents andlor pending patents.
TEKTRONIX. TEK. SCOPE-MOBILE. and @ an
registered trademarks of Tektronix, Inc. TELEQUIPMENT
is a registem trademark of Tektronix U.K. Lim~ted.
Printedin
U.S.A. Specification and pricechange privileges
are resewed.
INSTRUMENT SERIAL NUMBERS
Eachinstrument has a serialnumber on a paner insert, tag,
w stamped on the chassis. The first number or letter
designates the
muntry of manufacture. The last five digits
of the serial number
are assigned sequentially and are
unique to
each ~nstrument. Those manufactured m the
United States have six unique digits. The muntry of
manufacture ts identified as follows:
BOOOOOO
Tektronix, Inc., Beaverton. Oregon, USA
100000
Tektronix Guernsey, LM., Channel Islands
200000
Tektronfx UnitdKingdom, Ltd., Mn
300000 Sonyflektmnlx, Japan
700000 Tektronix Holland, HV, Heerenveen,
The Netherlands

TABLE OF CONTENTS
SECTION 1 CHARACTERlSTlCS
Gemllnforrnation
Eleetrieal
Characreristlcr
Vertical System
Horizontal System
EnvironmentalCharaEteristics
SECTION 2 BASICSEQUENTIALSAMPLl NG PRlNClPLES
InWoduction
Equivalent-Time Sequmtial Sampling
Vertical Func~mr
Horizontal Functions
Glossary of Sampling Terms
SECT ION 3 OPERATlAIG INSTRUCTIONS
Genwal lntorrnation
Mainframe
Controls
Getting
A Trace On Sween
Front Panel Controls
Other Plug+lnr
SECTION 4 APPLlCATtONS
lntroductlon
Phaso Differem Mearummenis
X-Y Phase kwremmts
Dual-Trace Phaw MeaswremmtJ
Time DifferenceMeasurements
Tw~Drn Memrements
Phaw Measurements Using the Two-Dot System
Pulse Width Measurements
Time
Between Pul* 'Using Dual Tram
SECTION 5 ClRCUlT DESCRIPTION
Vertical
System
Cornpenmeon Network
Delay Line
Sampling Gate
Sampling Gate Blaw-by Compensation
Strobe Generator
!%amplifier
DC Balance and DC Bdance Amplifier
Memory Gate
Memory Gating Generator
Memory Gate How-by Compensation
Memoly

TABLE OF CONTENTS (cont)
SECTlON 5 CIRCUIT DESCRIPTION (cant)
ht Memory Amplifier
Unity
Gain Inverter (Channel 2 Onlyl
OutputAmplifier
Switching
Vertical Power Supplies
Horizontal
System
Peak-To-Peak Signal Follower
HF SynChr~IIiXerOscillator
Trigger
Amplifier
Holdofl Ramp Generator
Trigger Circuit
Fast Ramps
Delta Delay Generam
Buffer
Scan Ramp Gating Multivibratw
InterdotBlanking
Pulse Generator
Inverter, Gating Generator, and Gated Current Generaor
kan Ramp nnd StaircaseGenerator
Two
Dot Circuit
Intensity Blanking Mixer
P~FtionVoltage Fdlower & WorimntalAmplifier
Readout
Horizontal
Power
SECTION 6 MAINTENANCE
Revcntive Maintwnance
General
Cleaning
Lubrication
Visual Inspeetion
Sern~mductor
Ch~ks
Recalibmtion
T roubfeshoot~ng
Troubleshooting
Aids
Component Identifieation
TroublsshootlngEqu~pmmt
TroubleshootingTechniques
Troubleshooting
Prmeduve
General
Test
Procedure
Horizontal Checks
Venieal Checks
Corrective Maintenance
Obtain~ngReplacement
Parts
SolderFngTeehniqu~
Cireuit Bmrd Replacement
Sampler Board Cwer Removal
Vertical Board Removal

TABLE OF CONTENTS (cont)
SECTION 6 MAINTENANCE (cont)
Sampler
Board Removal
Yertieal and Horizontal Interface brd Rernwal
Delay Line Removal
Compensation Board Removal
Trrggsr
Board 'Removal
Horizontal
Board Removal
Readout
Board Removal
Vertical
Made Switch Board Remwal
Component Replacement
Semiconductor Replmment
Connector Replacement
Push-button Switches
Rotary Sw~tches
Cam Switch
Recalibration
After Repair
InstrumentRe~knging
SECTION 7 PERFORMANCE CHECKSlCALlBRAT ION
Elementary
Checks and Incoming Inspection
DatailecE Checks and Adiustments
Equipment Required
Preliminary
Connections andSet-up
Power Supply Checks
Triggering Checks and Adjumnantp
Equipment
Set-up
Trigger Calibratian Check
Adjustment of R212 (Trig Gall
Sync Lwel Check
Adjustment of R530 (Sync Levdl
+ Balance and - Balance Check
Ad1ustment of R524 and R521 It Bal and - Ball
Sync Bias Check
Adjustment of R209 (Sync Bias)
Timing Cheeks and Adjustments
Equipment
Set-up
2-Dot Cal Check
Adjustment of R131 (2-Dot Calk
Delay
Stop Check
Adjustment of A130 [Delay Stopl
l pslDiv Delaying Check
Adjustment of R132 41 prlDiv Delayinn1
1 psfDiv Delayed Check
Adjustment of R460 I1 0rlDiv Delayed)
Scan Ram Check
Adjustment of R381 (Swn Ratel
Leadtime and Regist6-r Check
Adjustment af R472 and R230 (Leadtime and Regimr)
Delayed and DelayingTiming Checks
10 nslDiv, DelayingCheck
Adjustment of C350 (10 nrlDiv. Delaying1
REV. 0. APR. 1977
iii

TABLE OF CONTENTS (cont)
SECTION 7 CALIBRATION PROCEDURE (cont)
10 ndDiv, Delayed Check
Adjustment of C3Y (10 nrlDiv. Delayed)
Delayed and Delaying TimFng Varifieation
1 ns Linearity Check
Adjustment d R380 (1 ns Linearity)
Vertical Checks and Adiumnenta
Equipment Setup
Channel 1 Avalanche- Check
Adjustment of R20 (Avalanche for booth Channel 1 and Channel 2)
Channel 2 Avalanche Check
Delta t Center Check
Acljustment of R458 (Delta t bnter)
manner 1 DC Bafance. LoopGain. and Memory Batnea Cheeks
Adjustmt of R233, R232 and R242 (DC Bal. Loop Gain. and Memory Ball
Channel 2 DC Balanm, Loop Galn and Memory Balance Checks
Adjustment of R330. R331 and R344 ('DC Bal. Loop Gain. and Memwy Bart
Trigger Jither Check
Avalanche Recheck
Channel 1 L.F. Comparator Check
Adjustment of CH 1 R30 (L.F. Camp.)
Channel 2 L.F. Comparator Check
Adjusment ol CH 2 R30 (L.F. Cmp.)
Channel 1 and Channe! 2 Amplituclw AtmnuatFon Check
Channel f INPUT Connector Check
Channel
2 INPUT Connector Check
Channel 2 Amplitude Check
Channel
1 Amplitude Cheek
Readout
Checks
SECTION 8 ELECTRICAL PARTS LIST
Pam OrderingInformtion
Abbreviations
Crw Index, Mlr. Code Number to M.
Pam List
SECTION 9 DIAGRAMS AND CIRCUIT BOARD l LLUSTAATIONS
Block Diagrams
Vertical Block Diagram
Horizontal Block Diagarn
Electrim1 Schematics and Circuit Boards
Compensation
See Tabr
Trigger

TABLE OF CONTENTS (cont)
SECTION 9
DIAGRAMS AND ClRCUlT ROARD ILLUSTRATIOAIS Econt)
Vertical We SwltFh
Attanuatw Swiihm
Vertical
HolCzontal
Timing Switch
Vettiml InMm
Horizond Interfaes
Rdout
lntercennection and Power Distribution
SECTrON 10 MECHANICAL PARTS LIST AND MECHANICAL tLZUSTRATIONS

Mil INPUT
?W*CX
,-,.

Genaral Information
Section 1-7S14
CHARACTERISTICS
The Tektmnlx7S14 Dual Trace May& Sweep Sampler
is a general purpuse samplingunit with a DE-1 000 MHz
bandwidth. It will operate In any Tektrmlx 7000 Senes
mainframe. Tha front paneltem~nologyis similar to that of
convent~nalmc~llosoopes.
The
7514 has two time bases to provide "delaying" and
"delaved
sweep" 'ation. The ddaved sweep starts after
mints
is the productof the reading on the Delay Kme Mult
dial
times the DelayingSweep WDiv ming.
Delay lines inthe inputsignel channels permitdisplay of
the leading edge of the trigering waveform. The Auto
Level meprovides
a bright baseline in the absence of a
triggering signal. Other featurer indude 2mVldiv
sensitiviw, low tangential noise, versatiletr~ggetingmpabil-
itiss,
a broad range of sweep rate, and crt readout of both
the attenuation and timing values.
the
sttlected delay lyntenral, givingthe effect of a wide-range
sweep operation. The delayed sweep starts after the The characterirtics
given in the followingTableapplwover
selected delw interval, giving the
etfecf of a wide-range an ambient temperature
range from O'C to +W*C after €he
sweep magn~fier. The calibrated delay replam the "time imtrurnem
has been =librated at +25'~ t5'~. Under these
pos~tion" control fountl on most sampling time-baseunits. conditions, the
7S14 will pwform to therequirementsgiven
in the Performance Check section of this manual.
The
JS14 has a two dot time-interval mmsuremem
method
that prowdep a means of measuring the time The Supplemental information column of the Table
been two mints on the "normal" (delaying)d~splav. A provides additional information about the operation of the
brightened
dot on the trace can be m~t~onedto the start 7514. Characteristiu given in the Supplemental Infor-
of the event to be measured. A second brlghtend dot an mation column are not requirementsinzhernselves and are
be pdsit~oned to the end of the event bv using the Delay not necessarily checked rn the Performance Check
Time Mult control. The time interval between the two ~rocedure.
ELECTRICAL CHARACTERI!XICS
VERTICAL SYSTEM
I I
350 ps or Iesa, 10% to 90% of step pulse ]
I1
Step Aberrations
+2%, -3%. total of 5% or Teps P-P within made with Tektronix 284 Pulse
first 5 m after step transition;+l%. -3%. includes aberntiom from the
totat of
2% or less P-P thereafrer.
Bandwidth
(-3 dB) I DC to 1 GHr or more. ( Calculmedfrom risetime.
Accuracy
I Within 23% (with VARIABLE at CAP]. I
Input Reistance
DeflectionFactor
50 within 2%.
I
2 mVlDiv to 0.5 VIDiv. 8 stew, 4-2-5 sequence.
MaximumOperation 2 V P-P (DC +Peak AC] within a +2 V to
-2 V window at any sensitivity.
Variable
Input
Signal Range
At least 251. Extends urnlibrated deflection factor to
I approximately 800 pV/Div.
Maximum Overload *5 V.

Cha*aetsrholra-7S14
ELECTRICAL CHARACTERISTICS {cont)
VERTllGAL SYSTEM (mtF
HORIZONTAL SYSTEM
Delaying Tim Ease
-
Supplementd lnfwmation
Sourceresistam is 10 k0 N.).5%.
When input signal is 0.5 GHz sine wave.
Chmrecterlstica
name Raquir~nsnta
DC Offset Range .I to -2 V or more.
AT Range Shifts Channel I at least +1 ns to -1 m Range may be centered with internal
with respectto Channel 1. adjustment.
DisplayedHoisehangentiall
Low NoiwOperation
Venicd Signal Out
Dot Slash
lnterchannelCrosstalk
Delayed Tlme Base
2 mV or less, LOW NOISE switch "out".
Displayed noise reduced
by at least fiue
times.
0.2 VlDiv of deflsction *3%.
Less than 0.1 Div at 10 Hz and above.
-60 dB or less.
Time Base
Range
Tim Base Accuracy
Delay Zero Range
100 ps/Div to 10 nslDiv.
Within *2%. excluding first 'h division of
daplayed sweep.
0-9 divisionsor more.
fime Base Range
Accuracy
Variable
13 step, 1-2-5 sequence.
No time mark btween 1st and &h
divisions can be more than 02 divisions
from the major divisionlinewhen the 1st
mark is set on the 1st divisionline.
When Delay Time MultipIier
is set to
0.00, the 1st dot mn be moved past the
9th gmticule line.
DelayT~meMultiplier
Time between dots.
Delay
Accuracy
100 pdDiv to 1 W &Div.
Within
*3%, excluding first M division of
displayed weep.
At least 2.5:l.
Within 1% of full scraen 110 crtdivisiom)
when measurement is
mde between 1st
and 9th m divisions.
18 stem. 1-26 sequence.
No time mark between ist and 9th
divisions can be more than 0.3 divisions
from the major divison tine when the 1st
mark is set on the 1stdivisim line.
Extends uncalibrated TimelDiv to
ap-
proximately 40 ps/Div.

ELECTRICAL CHARACTERISTICS (cont)
HORIZONTAL SYSTEM (cant) .
Charactsrlstim
Triggering
Delaying Time Base
DelayedTime
Base
fime Base Display M&
Performarm Requirements
Conventional display, maxlrnum lead
time.
heft intensified dot indicates Time
Zero [Multiplier Zero). Right intensified
dot indicates
point at wkich Delayed
Sweep starts.
Erne between dots is read
from
the crt or the Delay Time Multiplier
dial.
Delayed sweep display
starts immediately
at end of delw time. Set by Delw Zero
plus Delay Time Multiplier. Operates in
same
manner as "run after delay" mode
Inwnventianal osciltoswws excem Time
Zero is adiustable and identifid.
NORMAL Triggered Mode
Supplemn4m! Information
Amplitude
Range
External
Internal
Input Resistance
Jitter
AUTO TRIG Mods (Auto baselinewhen not triggered)
TO mV to 2 V,P-P.
50mVto2V.P-P.
51 within *lo%, AC coupled.
Less
than 40 ps wrth 50 mV, 5 m width
trigger
at external input.
Less than 30 ps when internally triggered
from
284 pulse.
Sine
waves
Pulse
Minimum
Rise Rate
Rate of rise, 10 mV/ps orfaster.
At Sampler Input (vertiml input signal).
Rate of rise,
50 mVIvsorfaster.
150 kHz to 100 MHz.
TO Hz to 100 MHz.
10 mVIfis.
Sine waves
MinimumAmplitude
Pulse
Minimum Pulse Width
Minimum Rise
Rate
t50 kHz to 100 MHz.
TO mV P-Pat 100 MHz (Extl.
t kHz to 100 MHz.
70 nrat 1 kHz.
TO rnVlps.
Auto baseline below 800 Hz.

ELECTRICAL CHARACTERISTICS (cont)
HOR IZOPITAL SYSTEM (contl
HF SYNC Mode
Characteristics
Scan Controls
PerfonnanmRequiremenls Supplernentd
Information
Free-Running Sync. Sine waves
ENVIRONMENTAL CHARACTERISTICS
100 MHz to 1 GHz.
Repetitive
2540 Hz Repetition Rate.
Chatscteristics
Repetition rate barely into flicker rate.
Controls must
be set as follows:
Low Noise Control, out;
HF
SYNC Control, in;
Scan Control, fully CW;
Holdoffcontrol, fully CCW;
Delaying sweep- 1 pslDiv orfaster;
Approx~mately
20 samples per div at low
trigger
or sweep rates.
Dmcription
Scan Rate is the same as set in Repetitive
made.
Scan control serves as an attenuator. Full
stale s-n signal must run from OV to
+lo V or more.
Source resistance is 10 kn withrn 20.5%.
Single Sweep
Manual
Ext Scan
Maximum Sensitivity
Maximum InputVoltap
Horizontal OutputSignal
Amplitude
One sweep per Single Sweep Start burton
depression.
Scan control moves the spot over a
slightly greater range than 10 divisions.
1 VlDiv within k5%.
t50V.
1 VfDiv 15%.
Temperaf ure
Operating
Raw
Nonaperati- Ray
O"C to +50"~.
--40-C to t70°c.
Altitude
Operating
Range
Nan-perating Range
To
15,000 feet.
70 50.000 feet.
Vibration
Range
Shock Raw
Transportation (Non-operating)
To 0.025 inch peak-to-peakdrsplacement at 55 cycles per second.
To 30 g, %sine, 11 rn~llisemndsduration.
Meets National Safe Transit Test Requirements.

BASIC
SEQUENTIAL SAMPLING PRINCIPLES
Introduction
Sampling provides the means to display fast-changing
signals
of low amplitude tha cannot be displayed inany
other
way. Ssmpllng overcomes the gainhandpass limita-
tion inherent with conventional amplifiers and oscillo-
mpss. It does so by displ~ing a real-time signal in
"equivalent"
time. Only the input stage of a sampler is
subjected to the Input signal; all subsequent signal amplifi-
otion takss place through relativel~low bandwidth
amplifiers.
Sampling,
howaver, does require repetitiveinputsignals.
Fortunately.
most fractional-nanosewnd rrsetime signals
exist In low implance enwlronmmts; thus they may
be
delivered dlreetly through 50 ohm ~ables to a 50 ohm load.
They are wnwally low amplitude signals, so E4 ohm
atrenuators are
used when the signal is more than one or
two volts.
There are three types of sampling: sequential. random,
and real-time.
The 7514 uses the sequential sampling
method; this technique will
be discussed in this section of
the manual.
Equivalent-time Sequential Sampling
me sampling system looks at the instantaneous ampti-
tude of a signal during a specific small time period.
remembers
the amplltvde, and displays a single dot on the
at that mrrespnds to the amplitude. The horizontal
pxition
of the dot represents the equivalenttlme when the
sample
was taken. After a dot is displayed for a fixed
amount of time, the system again looks at the instanta-
neous amplitude of a d~fierentwcle of the input signal.
Each suwaseive look. or sample, is at aslightly later time in
relation
to a fixed pointof eeeh sampled signal wde. After
many cycles of the input signal, the sampling system has
reconstructed and displayed
a single facsimile made up of
many aarnples, esch sample taken in sequenee from a
different cycle of the input signal; thus, the term
"sequential sampling".
Because
the reeonraucted signal is not curnplewd until
long after
the first signal wcle has
occurred, it is
not
displayed in "real" time. The tlme displayed on the crt is
termed "equivalent-time".
Such a display ir shown in
Fig.
2-1. The equivalent time between dots is determined
by the time delay between the fixed point on the signal at
which sweep triggering occurs and the point at which the
$ample is taken, The real-timeand equivalent-timerelation-
ship is depicted In
Fig. 2-2. S~nceboth time references
(triggering and sampfing) are taken
from the same wcle of
the signal, the signal repetitions do not have to be Identical
in amplitude, timeduration, and shape. Periodicdifferen&
in indluidualn/cla,
however, will show as noise or jitter in
the remnstructeddisplay ifthe
shape or amplitudechanger
from wcle to cycle.
Tho number of dots per horizontaldivisioninone wveep
is called dot density. Sinm only one sample is taken from
any particular input
cvcle, the time needed to remnstrm a
display depends on the dot dmsiw and the repetitionrate
of the signal, The greater the dotdensity andthe slower the
repetition rate.
the longer the time to construct the
equivalent-time display.
Sampling swterns haw maximum signal repetition rates
at which samples an be taken and accurately display&.

Barlc Sequential Sampling Principb7S14
I
'T' Firn Lmph M Bmpk TJun mt Nm Ssmpls
Thn Han thlr hint on Wmform Takm Here
Fk. 2.2. Rd-time and aquivslant-tlma ralalmlp.
The primary limit is the time needed for the yertieal
amplifiers to stabilize after a sample has been taken. For
signals with arepetitionratshigher than 30 kHz. the timing
unit holds
off retriggeringfor a maximunof approximately
=as. This means thal a sample w~ll not be taken from
wery wcle of a high repetit~onrate signal: only those
cycles
are sampled that occur aftw the end of the trigger
holdoff. If the s~gnalis truly repetitwe and
each cycle is
identical.
these "mlssed" cycler ara of lirtle significance.
Signals Mow
30 kHz may have mnsidwable repetitive
rate jitter. but the ramfling oscillosmpe can still g~ve a
sample of each cyde without d~splayjltter because trig-
geringand sampling
both occur on the same cycle.
Vertical Functions
The sampling oseillosmpe's vertieaf stages perform the
same basic
funaions as those in a nonsarnpling oscillo-
mpe: i.e.. signal amplification and attenuation. Vertical
signal delay is
alx, used to permit viewing a signal's leading
edge.
All the amplification md signal pr-sing in the
mmpIing oscillosmpe {exmpt for the passive 50 ohm input)
is done
at relatively low frequencies. It is thts feature that
makes the samplingoscilloscope unique i.n performance and
design .
Sampling begins with the input signal being hangad to
stored, long duration, low frequency voltages mnsisttngof
brief portions [samples)
d the input. This change is nor a
frequency conversion; rather, it is a different way to
represent the inputsignal.
The sampled
enwgy is stored in a memory cirwitso that
it stays Eonnant between samples. Each time a new sample
is taken. the mmMy io refreshed. The amount ofsampled
and stored
energy represents the amplitude of the input
signal
when that sample is displayedon the aZ.
Vertical stages in a sampling cncillorcope include -me
nut found in a nonsarnpling oscillosmpe. sub as a
Sampling Gate, Blow-by Compensation, Preamplifier.
Memoty Gate, Memory Amplifier and Feedback, and
Memory Gatlng Generator. C~rcuitdescrimions for these
rtages appear in Section 5. In surnrnarv. stage purposes
are: Sampling
Gate samples brief portrons of the input
signal; Blowby Compensation nutlifi~unwanted signal
wupling; Preamplifier and
Memory Amplifier and Feed-
back keep the Sampling Gate output and Memorywnstant
between samples. making the Sampling Gate output propor-
tional
to ~tsinpwt; the Memory Gate passer the sampled
signal to the Memory; and the Memory Gating Generator
*urns on the
two gates.
An important mrt of the sampling proms is asampling
bop.
This loop provides in-phase feedback of the sampled
and memory mergy to the Sampling Gate output.
The
feedback forms a null-saeking servo loop thaattemptsto
make a zero difference between the Sampling Gate input
and output.
When the gain of the fedback loop is unity, it
mrnpensates for the attenuation across the SamplingGate.
In this
me. the feedback voltage equals the value of the
sampled inputsignal voltage. When the loopgain is Iss than
unlty,
the feedback voltage 1s less than necessaw to
equalize
the voltage across the gate. The Memory output
and feedbadr w~ll then approad the signal asymptotimlly
after several samples have
been taken. The Memory output

Basic Sequential Sampling hinciple~7S14
is effectively
a rnovmpl auerap of several preceding samples.
When the loop pin is greater than unity,
the feedbad
voltage
IS greater than the Sampling Gate input signal. The
result~ng crt display of a step signal input will alternately
ovetshoot and undershoot for
a few samples. For the least
display d~stortion.the loopgain must
be unity, allowing the
system to hack the input signal as closely w pss~ble.
A loop win of less than unity can be useful. if the
resulting wndition is undrnstood
and the system is oper-
ated properly. Randomnoise inthedisplay is reduced when
loop wrn IS less than unity, srnce several mnserxltlve
samples are averaged.The averaging,however. will slow the
risetime of
an abrupt step signal depending on the number
of dots in the step transition and how much kss than unity
the loop $am may be. Averaging will also reduce the
amplrtude of a sine
wave if there are not enough dots per
cycle.
When the memory gats is own, it paras the sampled
signal and
charger e capacitor inthe memory gate output.
This stored charge remains essentially Eonstant until an-
other sample is
taken. The memory output is not reset to
zero after
a given sample, but is held at the level of the
previous sample by the feedback signal.
In the memory gate output
there is a LO NOISE control
mat reducss the random no15e seen
al highsensitivities. The
function of th~scontrol is known as "smoothing," inthat it
smoothes or averages several mnsecutiw samples. A check
for whether smoothing is producing any distortion is
ammplished by incxeaslng the number of dots in the
display withthe
SCAN mntrol and observing whether there
isany signlfimnt change
in thewaveform.
Fig. 2-3 shows the usual effects of smoothing for two
different sampling densities (sampling density or dot
density
is the number of samples or dots per horizontal
division).
'Displayed
Fig 2-3. Equiualant.tlms display with and without umrohinq fw twditfersnt aampliq densities

Basic Sequential Sampling Principles-7ST4
The signal out of the memory gate gets, amplrfied by the
memory circuit.
Each change in voltage at the memory
output
is a step change proportional inamplitude toa step
at the inputto the prearnplrf~er.
On sampling systems havrng
two input channels, such w
the 7S14, there are two sets of sampling-loop crrcuits. The
wtput from each of the memories is
fed to a channel
swrtchrng multivibrator that selecfs which output each dot
represents,
sa that either channel can be displayed, or so
that both channels can be displaved, as two traces, by
alternating outputs witheach successivedot.
Horizontal Functions
The Horizontal system provides deflection volrage for
the cn display and s~multaneouslymntrols the time at
which the vertical system samples the input signal. The
system
us- (1) a 1 GHt trigger cwcurt, (21 two fast ramps
for either Delaying
sweep or Delayed sweep operation, (3) a
combination scan ramp and staircase generator to provrde
horizontal deflect~on
and a comparison level for the fast
ramps.
(4) two intensified positronable dots to provide an
accurate dial readilut for trme measurements and (5) a
delay generator to provide strobe dr~veto the two vertical
channels
so thar the signal st one input channel may be
sampled mnsistenrly earher than, later than, or coincident
withthe signal at the other Input
The sampl~ngoscillosc+lpes's horizontal sweep IS pro-
duced
by a staircase wltage that advances one step each
time a sample IS taken. One cycle of the input srgnal causes
the trigger circuit to in~t~ateone cycle
of the sampllng
process
and produce one dot for thedisplay.
The wrnpling cycle starts when the trigger circuit
recognizes a point in a cycle
of the triggering signal and
unclamps the fast
ramp generator. The fast rampgenerator
produes
a linear rundown voltage that is compared to the
slowly changing staircase voltage. The resulting pulse that
occurs the instant the fast ramp voltage level equals the
staircase voltage level
IS sent to the vertical circuit via the
Delta Delay Generator
as a strobe drive pulse. From there
the strobe also goes to the Scan Ramp and Staircase
Generatoras a sta~rcase-advancepulse.
The staircase generator advances one step ju~tafter the
sampling circuit takes a sample of the input signal.
The
sampling memory output isapplied tothe venical amplifier
and the naircase output level is applied to the horltontal
deflection system oftheoscilloscope.
AS smn as thesample
has
been taken, a dot is displayed on the crt screen at a
vertical position woportional to the input signal voltage
level
at the instant ir was sampled. The dot then remains
stationary onthe screen untilanothw sample is taken.
Each subsequent rec~gnisedtriggering signal cycle In,-
tiates the same sequence of events. But since the stairwoe
voltage moves down one step each tlme, the fast ramp has
to run slightly farther each time before
a comparison pulse
is produced.
In rh~sway the sampling event is delayed by
successively longer intervals and the samples are taken
successively later along the waveform with respect to the
triggering point. Each time a sample is taken, the
crt is
blanked momentarily while the dot on the crt
moves
horizontally by one increment.
The 7S14 comains a "twodot circuit" that provides two
brr&t dots for
each trace. With the two dot circuit it is
possible
to position the dots to two specific points in the
waveform and measure thetime interval between the points
directly fromthe 2nd dot positioning mntrol.
Glossary of Sampling Terms
There are manv terms used inthe discussion of sampling
systems whose
definitions may not be universal. The
following terms,
used inthis manual, have been mmpiled to
help avoid confusion.
Blow-by-A display aberration resultingfrom signal-induced
displacement current through all capacitance shunting
the Sampling Gate.
Display
Window-The particular time interual representxl
within the horizontal limitsof thegraticule.
Dot-A displayed spot indicatingthe horizontal and
vertical
coordinates of a particular sample.
Dot Density-The number ofdots per horizontal division in
any one scan.
Equivalent Time-The time scale represented inthedisplay
of
a sampling oscllloswpe operating in the equivalent-
tlrne sampling
mode.
Equivalent-time Sampling-A sampling prooess inwhich a
least one repetltlve signat event is required for each
sampletaken. The trme requited for display construction
is Thus greater than the tlme represented Inthe display.
REV 0 OCT 1980

Basic Sequsmial Sampling Principb7S14
Fert Ramp M Slewing Ramp-A linear ramp which acts
with a slower staircase. ramp, or other changing voltage
to cause slewing.
Feedback-The effective intersample attenuation in the
signal path
between Memory output and Sampling Gate
output in
a sampiing loop.
Forwad Gain-The effective gain between the Sampling
Gate output
and Memory output in a sampling loop.
Loop Gain-The product of sampling efficiency, foward
gain
and feedback attenuation In a sampling loop. Loop
gain is normalFy unlty except in
a smoothed display
where
it may be less than unity.
Memory-A circuit which stores the vertical (or horizontat)
mordinatsvakue
of a samDle.
Mamoly Gate-An electronicswitch between a Memory and
itsdrivingamplifier.
Retrier-A trigger signal which occurs before a relate$
signal
went.
AwlTime-The time scaleassociatedwithsignal events.
bmpling-A process of sensing and storing one or more
instantaneous duesof
a signal for further processingor
display.
Sampling
Efficiency-The ratlo of the valtage change
between the rnstant before sampling, t-, and the instant
after sarnpl~ng,
t*, at the output OF a Sampling Gate to
the difference &tween gate input voltage,
E,, and gate
output voltage.
E,, at the rnstant before sampling.
Sampling Gate-An electronic
wit& which conducts
briefly upon command for the purposeof mllecting
and
storingthe instanraneous value of a signal.
Sampllng Loop-Those circuits providing the main signal
path through the Sampling Gate, Preamplifier.
Lmp
Gain attenuator, OC Balance Amplifier, Memory Gate,
Memory, and the Feedback attenuator.
hnning-The promss 'by which slewing is controlled.
Sequential
Sampling-A sampling process inwhich samples
are taken at succsssively later times relative to a fixed
point of each sampted signal cycle.
Slewing-The procsss of causing suocessive samples to
b$
taken at different instants rekat~veto a fixed point of
each sampled signal cycle.
Smoothing-A precess that reduces the
effect of random
noise or jitter
in the display by averaging several
mnsecutivesamplH.
Stmbe-A pulse of short duration which operates the
Sampling Gate.

Section 3-7S14
OPERATING INSTRUCTIONS
General Information
The 7S14 is a double-widthplug-in unit mntaining both
vertial and horizontal deflection Brcuits. The 7S14
opamtes inany Tektronix 7000 Series mainframewhen the
unit is cornpletel~inserted into the proper two slots of the
mainframeplug-in compartment. When inserted into main-
frames that accommodate rhree sirgle-wdth plug-ins, the
twe slots toward the operators right should be used. The
middle two dots should be used infourhole mainframes.
NOTE
lWren thc 7S14 is umd in die R76d3, R7613, R7623,
or R7903 rackmount iflmments, the wrppoff posts
&wen the mkmount plug-in com~mmts must
be remd w that the duaI width ?Sf4 can be
inserted into the rnainfm.
A blank plug-in panel may be used to cover the opening
of any slot not occupied by a plug-in unit. Use panel
01641 5500 for 7000 Series rnainframm.
Assuming it ir clean and dry, the plug-inunit is ready to
operate
as soon as ~t has been wrrmly installed in the
ma~nframe.Hwrwer. the mainframe
power cord must first
ba plugged into a meroutlet that supplier AC voltageof
the Eorrect frequency and amplitude and the rnainfram
pwrer nrr~tch
rnw be turned on. Itshouldnot be necessary.
to turn the wer off before removing or inserting the
plug-inunit.
Mainframe Controls
Wide the pcww switch, there are other swltcttes and
mntrols on the mainframe that must be set for the 7St4 to
operate mrrectly. If you are not already familiar with the
functionsof
the mainframecontrolsvou mav needto refer
to the instruct~enmanualfor that mainframe.
Getting A Tram On Sereen
With paw& applied and the plug-in properly insart&,
the next
step is to get atrace on ween. The recommend&
procedure
is to (I] temporarily dismnnea any vertical
input or trigger input srgnals,
(2) dect the repstitive pc%n
mode by pushing the REP button, (3) select l~s per
division or faster for the DELAYING SWEEP (dark gray)
mntrol,
(41. freecun the time baw and samptlng circuits by
~sh~ngthe AUTO TRIG and HF SYNC buttons. I51 select
Channel
1 Venial input by pushing the CH 1 button, (6)
set the Channel 1 VOLTSlDlV mntrolto the leastsemit~ve
position. oounterclockwise
to .5 V, (71 center the
Channel1
QC OFFSET mntrols. and (8) adjust the
mainframe crt intensity control for a medium brighttrace.
If atram doen not appear under these wnditions. it is likely
that either same ma1nfram.smntrolwar incorrectlv
set, or
that Ehs mainframe or plug-in unit is not functioning
PW~~Y.
A brief description of the pubpse and use of each fmot
paner mnnector, pushbutton, wnml, and serewdriwr-
adjustment
on the SS14 follows. Ifyou hwe neveroperatsd
a sampling osillom,
you should re& the entiresection
More
pmceed~ng to display a signalwaveform. Yw should
refer
to Fig. 3-1 as a guide ta specificopwatinginstructions
relating
to each front panelcontrolor connector.
1. 50 n INPUT The% are input mnnectoroto both
f5 V MAX Channel I and Channel 2 mrnpting
gate circuits and
uertiwl ddfection
amplifiers. Signals
as large as 2 V
A-F rn amplitude may be handled.
as long as no wing exds +4 volts
or
4 volts. However, peak signal
excursions that
exmed 42 uoltr or
-2 volts cannot be d~splayedat the
more sensitive setting, even when
using maximum DC OFFSET. Volt-
sge greater than f5 volts may alter
the accuraw of pr6crslondelay line
mmpensation rpsi%tors
or cause
input c~rcuitmmponents to fail.
External pr- or
50 ohm amnua-
tors should
be used to displaysignal
uoltages greater than
4 volts. The
following probes are recommeded:
P6056, 10X probe; P6057,
IOOX probe;
P6201. 1X. 10X and
lOOX FET probe. You will need a
1101 Poww Supply for the P6201
wobe I$ the ma~nframe does not
have a probe power output jack.
The
BNC 50ohm attenuators
recommended are:
011-M159.02
(IOXl, 01 1-0080.02 (5x1, and
01 1 .W60-02 12X I. Signals as great
as 220 wlts peak or 14wlts RMS
may be appliedtothese artenuators
befare %%dingthe watt*
rating.
50 ohm attenuators having
mnnenors other than
the BNC
type may be udif darners to
BNC mnnectorsare available.

Operating InnructionkTS14
2. CH 1 The nuter mnrrol SPIPMS the wr. 3. DC OFFSET
VOLfSrOlV tical deflection factor from ?2 V
and
.5 VlQiv to 2 mVIDlv. The red var,
CH 2
able control (CAL) udjusls sensitiv-
VOLTSlDlV
ity over a range of a1 lcast 25 to 1.
The rwo controls prov~de any scn
srtlv~tybetween 5 V Qer d~vls~on
and 8 mV per division. he CAL
mntml must be set In the fully
coun~erclockw~seIdetented)
posltlon
before the lnd~cated de-
flectlon factor can be expected to
be accurate.
These two controls posltron the
dqsplar up or down or Ws1t101l a
srgnal an screen that othenulse may
he off screen. A signal rlding on a
DC level as great as +2 uolta or
-2 volts may be wsitioned to
center screen. The FINE control
makes it easler to pr~cqsely position
?liedisplay at h~ghsensirlvttles

Operating Imhu~tmns-TSl4
4. CH ? GAIN Thm screwdriver adjustments sm
and '
the gain of the wrresmnding&an-
CH 2 GAIN nels so that the chosen deflection
factor correspondsto the deftemion
displayed
on the m by a signal
voltage
of known amplitude. For
example, a signal of precisely 1 volt
P-P amplitude should lproduce five
divisions
of deflection when the
VOLTSlDlV
is .2 V. Each adiust-
mant should normally
be checked
each time a plu~in rs placed In a
different mainframe.
he applied MI voltage
should be fmm a 500hm
soume so that he lettap
miving st the input may be
one half of the open
circuit, unloaded voltage 9. CH 1 Y
value. CHZX
Push this button to display a signal
at Channel 1 input.
Push this button to displav a signal
a Channel 2 input. There is no
internal slgnal pi&oH horn Chan-
nel
2 input; internal triggering is
from the signal picked off from
Chmnel
1. Therefore, if you have
only one input srgnal
it should be
connectedto CH 1 inputunlessvou
use
an external trimer input signal
or using a pwverdlurder, first divide
the signal so part may be appliedto
the external trrgger input
jack.
7. DUAL TRACE
Dual trace operation is achiewd by
pushing both CH 1 and CH 2
buttonsat the same time.
8. ADD
.Pushing the ADD button allowsrhe
and signals
at CH 1 INPUT and CH 2 10. LO NOISE
CH 2 tNVERT INPUT to be, in effect, summed.
Actually,the summing owation is
performed on the sampled replieas
of the
two rnput signals following
the vertical channel memorier.mis
button should normally
be pwhed
when
two balanced, pushgull $19-
nals are applied to the CH 1 and 11. CH 1
CH 2 INPUTS. You may then also TlME DlFF
push the CH 2 INVERT button to
CH 2
achieve, in effect, drfferent~alInput
operation.
Or, if you wish to me
how s~milarthe two halves of the
~nhgullsignal
may be, any differ-
ence
between them can be dis-
played by leaving the CW 2 IN-
VERT button out.
To display
the difference betwen
two similar signals that have nearly
the same wlarity or phase and the
aame amplitude, the CH 2 INVERT
button should be pushed.
NOTE
A front pvwrei xrewdrivw
adjustment (CH I-TIME
DIFF-CH2I can be sret for
wry precise phase or time
mmparisons. Refer to a later
discussion of the purpom of
ha at control.
This button should be pushed for
X-Y displays, such as Lisajous pat-
terns. The signal appl~ed m the
Channel
1 inpvt produces vertical
deflection
(V) in the normal way
and the signal applwl to the Chan-
nel 2 input produces horizontal
deflection
[X). When using this
mode. neither the DELAYING
SWEEP
nor DELAYED SWEEP
controls
affect the display in any
way. except to change the max-
imum possible number of samples
per mnd. Set the DELAYlNG
SWEEP time per division to 10 ns
and th% triggerlng HOLDOFF con-
trol fully munterclockw~se
ta
ensure the geatest possible number
of samples per second. The cleanest
X-Y displays are achieved by trig-
gering or
synchronizing in the usual
way before pushing the CH 1
YCH 2 X pushbutton.
Push this button to reduce the
amplitude of random noise in
the
dlsplay or. in some me$, to reducs
bor~zontaltime-lmer. It is normal
for the horizontal scan
rate to
reduce greatly
when this button is
plshed.
This screwdriver mntrol &ould
normally
be set {and is set at the
factory) sa that identical signals
applied to
the two inputs will b
displayed in precisely th% aame
hor~zontalwsltions. For example,