Tektronix 321 A User manual

IVIAIMUAL
Tektronix, Inc.
S.W. Millikan Way •P. O. Box 500 •Beaverton, Oregon 97005 •Phone [phone] •Cobles; Tektronix
070-425 564

WMRMiTY
All Tektronix iMtriMiMts ore warranted
Oflainsl defective materials ond workman-
ship for one year. Tektronix trontfermen,
mottufactured in our own plant, are wor*
rooted for the life of the instrument.
Any questions with respect to the wor-
ranty mentioned above should be taken up
with your Tektronix Field Engineer.
Tektronix repoir and replacement-part
service is geared directly to the field, there-
fore all requests for repairs and replace-
ment parts should be directed to the Tek-
tronix Field Office or Representative in your
areo. This procedure will assure you the
forest possible service. Please inclede the
inctrument Type and Serial number with all
requests for ports or service.
Specifications and price change priv-
Ueqes reserved.
Copyright ©1964 by Tektronix, Inc.,
Beaverton, Oregon. Printed in the United
States of America. All rights reserved.
Cdetents of this publication moy not be re-
produced in ony form without permission
of Ihe copyrightowner.

1CONTENTS
Worronty
Section 1Choracteristtes
Section 2Preliminary Instructions
Section 3Operofiao. Instructions
4Circ^iff^ description ,
Section &; Mointencmee
Section 6Calibration
Section 7Ports Lirt .fimd .-Diograms..
Alis( of abbreviations and syndaols used ifi tbK
manual will be :^found on page 7*1. Change
(nformotion. if ony, is looted at the rear of the
monuol.

notiiONiAi
AOtl'lON
vItTiCAt
rO»iiiOa
iiAIIA»ll
TIME/DIV
TIME
VEftTlCAl
AMPLIflER VOITJ/OIV
Type 32) A
TK» 331 AOvCillOsc^^*

Typ« 321A
SECTION 7
CHARACTERISTICS
Introduction
Th« Tektronix Type 321 Ais ahigh-performance, dc-to-6
me, tronsistorized oscilloscope. Its light weight, small size
and ability to operate from avoriety of power sources make
it aversotile field and laboratory instrument. The oscillo-
scope can operate from its Inletnally-contoined rechorgeable
battery pock, an external dc source or from o115/i^-volt
50-800 cycle ac line. Reguloted power supplies in the instru-
ment, accurote colibrotion, ond precise linearity ossure exact
lime and omplilude measurements despite normal voltoge-
source and power-supply-load chonges that occur under
octuol operoling conditions.
Operotir>g temperature range derived from tests indicates
optimum performance ond reliability on its self-contained
batteries from 0* to -t-40* Cat altitudes up to 15,000 feet.
Temperoture range without botteries when operating from on
externol source is -—15' Cto -4-55* C. Non-operating tem-
perature range is —55* Cto +75* Cwithout botteries
ond —40* Cto -|-50* Cwith batteries at altitudes to
50,000 feet.
for the operotor's convenience, afront-panel bottery light
indicotes when the internal batteries are low. If exterrtal dc
or ac operation is being used insteod of the botteries, the
light turns on if the external voltoge source drops too low
for proper power supply regulation.
A4-position power switch on the front panel permits
convenient selection of charging rote ond/or power source.
Vertical Deflection System
Bandpass—Dc to at least 6me (3-db down) using dc cou-
pling; using oc coupling, low-frequency 3-db down point
is 2cps lypicol from oI-kc reference.
Sensitivity—0.01 v/div to 20v/div in II calibrated steps;
accuracy is within 3% of fronl-ponel markings. Con-
tinuously variable from 0.01 v/div to oboui 50 v/div
uncolibroled.
Input Impedance—35 pf nominal paralleled by 1megohm
8.2 pf nominal paralleled by 10 megohms
i'±:2%] when using the P5006 10X Probe.
Maximum Allowable Input Voltage Rating—500 volts com-
bined dc ond peak oc; 500 volts (not 1200 volts) peok-lo-
peak oc.
Triggering
Type—Automatic, or ompliiude-level selection using pre-
set stability.
Mode—Ac-coupled or Dc-coupled.
Slope—Plus, from rising slope of triggering woveform, or
minus from negotlve slope of triggering woveform.
Source—Internal from verticol signol, or external from
triggering signal.
Signal Requirements—Internal; 0.2 major division verticol
deflection ol Ikc increasing to 1major division at 6me.
External; 1volt peak-to-peok ot 1kc increasing to 3volts
peok-to-peok at 5me. Nominal input impedance; 5pf
porolleled by 100 kilohms (:±30%).
Sweep
Type—Miller Integrotor.
Sweep Rotes—O.Sftsec/div to 0.5$ec/div in 19 calibrated
steps Accurate SX sweep mognifier extends calibrated
rartge to 0.1 fisec/div. Calibrated sweep-rote accuracy
IS -tr3%. Sweep lime adjustable between steps and to
>1.5sec/div uncollbraled.
Extemol Horizontal Input
Bandpass—Oc to ot least 1me (3-db down).
Defleciion Foctor—1v/dv ±10% with 5X mognifier on.
Input Impedonce—30 pf lypicol porolleled by 100 kilohms
(±5%).
Amplitude Calibrator
Square Wove—Frequency about 2kc.
Amplitude—500 mv peok-topeok. Also 40 mv peok-to-
peak Iniernolly coupled in CAL 4DIV position of VOLTS/
DIV switch. Peok-lo-peak amplitude accuracy is ±3%.
Cathodo'Roy Tube
Type—Spedol Tektronix-monufactured T32I1. 3" flat-face,
post-deflection accelerator. Low heoter power.
Accelerating Potential—4kv.
Z-Axis Modulation—External terminal permits RC coupling
to ert grid.
Unblanking—Deflection unblonking.
Phosphor—Type P31 normally furnished; PI, P2, P7, and
PI1 phou>hors optional. CXher phosphors furnished on
special order.
Graticule
llluminotlon—Vorioble edge lighting when operating from
oc line.
Display Areo—Marked in 6-verticol ond 10-horizontal V/'
divisions.
Power Requirements
Source—Operotes from 10 size Dfloshlight cells, or 10
size Drechargeable cells (opproximotely 3hours using
2.5 ompere-hour cells; approximately 5hours using 4
1>1

ChorocterisHcs —Typ* 321
A
omp«r«-hour cells), or 11^ to 35 volts dc (aircraft, outo,
boot, etc.], or 103.5 to I2d.5 volts or 207 to 253 volts,
rms, SO to 600 cycles, single-pbose oc.
Power Consumption—Approximately 700 ma from iniemol
botteries or externol dc source; 20 wotts nominal ot
115-volt ac line.
Temperature Protection—Thermal cutout switch interrupts
power if ombient temperature exceeds 131* F(55* Q.
Built-in battery chorger is liondard equipment.
Environmental Copobilities
Vibrotion (operating)—0.025" peak-to-peok, 10 to 55 to
lOcpi in 1minute sweeps (4 G's] for IS minutes on
each oxis. Three-minute vibrotion at resonance or
5Scps on eoch oxis.
Shock (operating]—20 G’s, Vs <>ne, 11-msec durotion.
Two shocks each direction along eoch of the three
mojor oxis: bottom, top, left side, right side, front
nd reor. Total of 12 shMiu.
Shock (non-operating)—60 G's, Vj sine, 11 -msec dura-
tion. One shock each direction olong eoch of the throe
major oxis; total of 6shocks.
Humidity (non-operating)—Meets Mil-Std-202B, method
106A (except freezing and vibration) through 5cycles
(120 hours).
Tronsit (non-operating)—Meets Notionol Safe Transit test
when foctory pockoged. Vibrotion for one hour at
slightly greeter than one G. Eighteen-inch drop in ony
orientotion.
Mechanical Specifications
Construction—Aluminum olloy chassis ond cabinet.
Finish—Anodized panel, blue vinyl-finish cabinet.
Dimensions—B'/j" high, 5V4"wide, 16" deep overall.
ACCESSORIES
Information on accessories for use with this instrument is
included ot the rear of the mechanical parts list.
1-2

SECTION 2
PRELIMINARY INSTRUCTIONS
Power Requirements
The regulated power supplies in the Type 321 Awilt operate
form 115-v or 230-v rms oc line, from on exterrtol dc source
(11.5 to 35 volls), or from a"boUery pock "consisting of
either 10 size Dflashlight cells or 10 size Drechargeable
cells.
Fuse Data
Use only the recommended fuses in the Type 321 AOscil-
loscope. The upper fuse, F521 (see Fig. 2-1), is oI.Samp
3AG Fast-6io; the lower fuse, FdOl, is a.25-amp 3AG Fasl-
Blo. Neither fuse needs to be changed if the oscilloscope
is converted from one line voltage to the other (115 vond
230 v).
Fig. t-l. L»eatlpn •! fu*»< and Chorgpr (latt-ild* vlaw).
Ac Operation
Unless tagged otherwise, your instrument is connected at
the foctory for operation at 103.5 to 126.5 volts, 50 to 800
cycles oc (115 volls nominal). However, provisions ore mode
for easy conversion to operate ol 207 to 253 volts, 50 to
800 cycles (230 volts nominol). The power transformer T601
is provided with split input windings which ore normally
connected in porallel for 115-volt operation, but which con
be connected in series for 230-volt operation.
The primary windings ore marked 1, 2, 3, ond 4. Terminals
1and 3ore connected to one winding and terminals 2and 4
ore connected to the second winding. The ac input leads are
connected to terminals 1and 4for both 115-volt ond 230-
volt operotion, so these connections do not have to be
chonged when converting from one line voltage to the other.
When wired for 115-volt operation, terminals 1and 2are
joined by abare bus wire, and terminals 3ond 4ore simi-
larly joined, as shown in Fig. 2-2(a). To convert to 230-
volt operation, remove the bare bus wires between these
terminols and substitute asingle connecting wire between
termirtals 2and 3, as shown in Fig. 2-2(b).
To turn on the Type 32IA when the power cord is con-
nected to the oscilloscope power connector and to the ac
voltage source, set the POWER switch to EXT ON. To turn
off the oscilloscope, set the POWER switch to TRICKLE. The
TRICKLE position can be regarded as the normal ’off" posi-
tion for the instrument
fo IIS-v AC
lb)
Fig. i-i. (at Trantfermar <ann«ti»n for oparaiion Irom 103.S-
134.Svolt ac lint; (bl ctnntclionc for eptrolien Irom 307-353
voll CK lint.
As long as the ac power cord is connected to the ac lino,
power is being applied to the power transformer T601, ac-
rectifier circuit, and grolicule lights for oil positions of the
POWER switch. Application of power lo these circuit is re-
quired to provide battery-charger operation for the internal
botteries; the groticule lights provide visuol indication that
these circuits are "on". Power to the bottery charger itself is
controlled by o Charger switch [see Fig. 2-1). If the switch

Preliminary Instructions —Type 32TA
IS set to lOW or HIGH, the ac rectifier is connected to the
battery charger circuit which, in turn, provides charging cur-
rent to the internol rechargeoble batteries.
NOTE
if dry cells are used instead of rechargeable bot>
leries, theri the Charger switch must be set to DRY
CELLS to disconnect the charger circuit. For further
information obout battery operation, refer to the
topics tilled "Battery Operation" and "Battery
Charger" appearing in this section of the manual.
if the Type 321 Ais being operated exclusively from the
ac line and the Internal batteries ore removed, the Charger
switch can remain in the DRY CELLS position to disconnect
Iho charger circuit. It you prefer to completely turn off
oil power to the Type 321 A, set the POWER switch to
TRICKLE and either disconnect the power cord from the
QC line or turn off the power ot owall switch (or equiv-
aloni|.
Ekittery Opergtion
Operotion from the internal battery source con be accom-
plished by usingr
1. Ten size Dflashlight colls (approximately ’/j-hour con-
tinuous operotion, more with intermittent operation), or
2. Ten size DAlkoline cells such os Evereody E95, Burgess
AL-2, or Mollory MN-1300 (about 2'/j hours continuous
operation], or
3. Ten size Dnickel-cadmium rechargeable cells (up to
about 5hours continuous operation, depending on the
type used).
The nickel-cadmium cells ore the most proctical type where
considerable battery operation is plonned.
To install the cells, first open the bottery cover as illus-
trated in Fig. 2<3. Next, install the boiteries by following
the procedure given in Fig. 2-4.
CAUTION
Be sure to observe celt polarity indicated on the
bollery cover.
To turn on the Type 321A when operoting from the internol
botferies, set the POWER switch to BATT ON. To turn off the
oscilloscope, set the POWER switch to one of the OFF posi-
hons-—FULL or TRICKLE. These OFF positions disconnect
the botteries from the OKilloscope load (10-volt regulated
supply! so there is no battery droin. To charge the recharge-
oble botteries, refer to the next topic tilled "Battery Charger".
wrtw fp vnl«(k
<QV«r, thftn pyM *p
Hg. 2*3. balt«ry <ov«p from Typo 321 AOKlll«»cop«.
2-2

Preliminary Intiructioni —Type 331
A
IntofiMl tenefy Termlital*
AC Paw«r
Core
Conn«ct«r
€irt«rr>ol
DC
C»An#<t#r
f. boHviy 4. Imtoll baW#fy <9v#f.
MfM ^Hry K»l4»r. Mr*
to obMWO coll polor^ «« In-
iicttd on 4feo cooor.
2-4. Pro<oduro for inttollln^ rti* bot1«ri*$.
Battery Charger
As mentioned previously, the battery chorger is connected
to the internal batteries as long as the ac power cord Is
connected to on ac power source and the Chorger switch
(see Fig. 2-1 )is set to HIGH or LOW. No chorging occurs if
the Charger switch is set to DRY CELLS.
Table 2-1 summarizes the charging currents Ihot can be
obtolned by using various line voltages in combination with
various settings of the POWER and Charger switches. The
table shows the Type 321 Awired for 115-volf nomlnol line
operation. If the oscilloscope is wired for 230-volt nominol
line operotion, the charging currents will still be the same
but the ac line voltages will be twice the amount shown in
the table.
Use Toble 2-1 as on oid in determining the proper posi-
tion for the POWER ond Chorger switches for the portlculor
brand or type of rechorgeoble batteries being us^ in the
Type 321A. After setting the switches to Iheir proper posi-
tion, the line voltage con then be set to the charging rote
recommended by the manufacturer of the cells. An auto-
transformer having arating of at least Iompere and
equipped with on rms-reading ac voltmeter con be used to
set the line voltage.
When using rechargeable botteries, sixteen hours of
charging at the full rated chorging current recommended
by the manufacturers should be odequate to fully charge
the batteries. Excess chorging may damoge the batteries.
One method for determining charge conditions of the bot-
teries is to set the POWER switch to BATT ON and then
meosure the voltage across the battery terminols (see Fig.
2-41- Areoding higher then 13 volts indicates thot the
botteries are fully charged. Areoding lower than 13 volts
indicotes that more charging time is required.
As mentioned previously, if dry cells arc instolled in the
battery holder and the Type 321A is being operoted from
the ac line, the Charger switch must be set to the DRY CELLS
position. This position disconnects the chorging circuit from
he batteries.
TABLE 2-1
Charging Currents
POWER' Chorger Aproximate Charging
Switch Switch Current in Ma
Kosilion Position 103.5 v109 v115v 121 v126.5 v
EXT ON LOW 20 24 27 j31 33
HIGH 22 26 30 I33 135
TRICKLE LOW 31 34 38 I41 44
HIGH 34 37 41 44 48
FULL LOW 160 1180 200 220 230
HIGH 290 ,320 360 380 410
*Tho ftATT ON poiih'OA it not Includoc^ in Iho loblt bocouio tho
Typo 22 1Aihogfd not bo operotod from tho oc line ond the
boMenos o» tho %omn timo. tooioni lottery drain exc««dt cHor9*
ing role.
2-3

Preliminory Instruction* —Type 321A
Oc Operation
Operation From an external dc source i* acomplished by
connecting >Fie special pigioil-type dc power cord in the
proper manner. For 11.5- to 30-volt operation, the black
l-fl and white |—)leods are connected to the voltoge
source; For 30- to 35-volt operation, the green |+| and white
(--') leads are connected to rho voltoge source. When the
connections to the externol dc voltage source are properly
mode, the external dc source is Floating with respect to the
Type 33IA chossis. Up to 600 volts diFFerence is permissi-
ble, if necessory.
To turn on the Type 321 A, set the POWER switch to EXT
ON. To turn oFF the oscilloscope, set the POWER switch to
one of the OFF positions—TRICKLE or F^LL.
When operoting From the externol dc source, the ac line
cord should be disconnected. That is, only one of the exter-
nal sources should be used rather than both at the some time.
NOTE
The internal bottery charger circuit Is disconnected
during external dc operation. Therefore, external
batteries (if used as the dc source) connot be
chorged by connecting the line cord to the ac line.
Also, on externol dc source cannot be used to
charge the internal batteries since the POWER
switch does net electrically connect the two
sources together.
LOW BAHERIES Ught
The LOW BATTERIES light turns on when the following
conditions exist:
1. The POWER switch is set to BATT ON ond the internal
batteries drop to 11.5 v(i:0.2 v) or lower.
2. The POWER switch is set to EXT ON ond the exterrial
source voltoge is low enough to cause the Type 321A un-
regulated voltage to drop to oboul II.Sv or lower.
2-4

SECTION 3
OPERATING INSTRUCTIONS
General Information
The Type 321A Oscilloscope is an extremely versatile In-
strument, odaploble to agreat number of opplications. How-
ever, to moke full use of the instrument, it is necessary thot
you understand completely the operation of eoch front-panel
control. This portion of the manual is intended to provide
you with the basic information you require. If you are
familiar with other Tektronix oscilloscopes, you should hove
very little difficulty in understanding the operotion of the
Type 321 A. The function of many controls is the some as
the function of corresponding controls on other Tektronix
instruments. Afront-panel view of the Type 321A is shown
in Fig. 3-1
.
Intensify Control
The INTENSITY control is used to odjusi the troce bright-
ness. This permits odjustment of trace intensity to suit the
ambient light conditions and changes in intensity coused
by changes in the sweep triggering rate (sweep duty cycle).
Clockwise rotation increases the intensity ond counterclock-
wise rotation decreases the intensity.
Focus and Astigmatism Controls
The FOCUS ond ASTIGMATISM controls operote in con-
junction with each other to allow you to obtain osharp,
cleorly defined spot or troce. To adjust these controls:
1. Adjust the INTENSITY control for the most pleosing level.
2. Set the ASTIGMATISM control to midscale.
3. Adjust the FOCUS control for sharpest detail.
4. Adjust the ASTIGAAATISM control as necessary for best
overall focus.
Graticule Illumination Control
The groticule used with the Type 321 Ais accurately
marked with 10 horizontal and 6vertical divisions, with 0.2-
division markers on the centerlines, These graticule morkings
allow you to obtain time and voltage meosurements from
the oscilloscope screen.
Graticule illumination is adjusted by the SCALE ILLUM
control, located just to the right of the oscilloscope screen.
Roioting the control clockwise increases the brightness of the
graticule markings and counterclockwise rololion decreases
the brightness.
NOTE
The graticule it illuminated or>ly when operating
from on oc line. This permits longer operation
when on batteries.
Positioning Controls
Two controls ore used with the Type 321 AOscilloscope
to position the trace or spot on the screen.
The HORIZONTAL POSITION control moves the trace to
the right when it is rotated clockwise ond to the left when it
is rotated counterclockwise. This control has opositioning
range of opproximotely 15 divisions with the sweep magnifier
off, and opproximotely 75 divisions with the sweep magnifier
on.
The HORIZONTAL POSITION control is acombination
coorse/vernler type of control. Built-in blocklash between
its two sections permits 30° of vernier odjustment for ogiven
coorse setting. If a30* range is exceeded, the coarse ad-
justment tokes over to provide fast positioning of the trace.
The VERTICAL POSITION control hos sufficient ronge to
position the troce completely off the top or bottom of the
screen, or to ony intermediate point. The troce moves up
when the control is rotated clockwise ond down with the
counterclockwise rotation.
Intensity Modulation
The crt display of the Type 321 AOscilloscope con be in-
tensity moduloted by on external sigrral to disploy additional
informolion. This is accomplished by disconnecting the
grounding bor from the CRT GRID connector ot the reor of
the instrument and connecting the external sigrrol to this
terminol. Anegotive signal of opproximotely 30 volts peak
is required to cut off the beom from maximum intensity, less
with lower intensity levels. Negotive-going signals as low os
5volts peak will accomplish intensity modulation.
HORIZONTAL DEFLECTION SYSTEM
Horizontal Sweep
The usual oscilloscope display is ogrophicol presentation
of inslontoneous voltoge versus time. Volloge is represented
by verticol deflection of the troce and time is represented
by horizontal deflection. To obtoin ouseful disploy, the spot
formed by the eleciron beam is deflected horizontally at a
known rote, so that any horizontol distonce on the screen
represents adefinite known period of lime. The trace formed
by the deflection of the spot across the screen is known os
the horizontol sweep. Since the horizontal deflection of the
spot bears odefinite relationship to time, and provides the
meons for making lime measurements from ihe screen, the
horizonlol sweep is olso known as the time base. (See Fig.
3-2).
The rale at which the spot is deflected ocross Ihe screen
is occurotely controlled by the setting of the TIME/DIV con-
trol. The setting of the TIME/DIV control determines the
sweep rate, and thus ihe number of cycles disployed on the
crt screen. The control is set to disploy ihe portion of the
waveform you wish to observe.
3-1

Opvrating Instructions —Type 321
A
HORIZONTAL CONTROLS
TRIGGERING CONTROLS
DC >Al fai f*n>nt
<k iMlarK* oi VtrMcsl Amplifier.
VERTICAL CONTROLS
CAL OUT SMMV—T*rm>n«l pro-
vldpi SOO-mT <qwer* w«y» for
(omponiotinp pcobo.
lEVEU—4«lo(n point on tiigeoting
tignol at which >woop l< trlggorod.
SLOK-*-4>otorniirtoc whothor iwoop
i« triggorod on 4or —ilopo of
Iriggoriiig olgnol.
AC>OC—Soloctt AC or DC ceupllitg
for triggoring lignai.
INT*iXT—SolocH oithor Intornal or
oxtornol triggoring •Jgnol.
FOCUS —Cenirolo thorpnoit of
ipol or ITCKO. \
ASTIGMATISM—Utod in ceniunt-
rion with FOCUS to obtoln ovorall
focin. V
CRT CONTROLS
INTrNSITT—»Centrelo brighlnoft of
tioco.
SCAU ILIUM—AdtvUi brightnoit
of groticult <notlilne> (whon opor>
otlng from AC llnol.
HORIZONTAL POSITION—Ceorio-
vomlor rypo of control Hiot poil-
flont traco heriientallv.
POWfft^Swilch tvmt rogulolod
IO*volt powor on artd off. Alto,
tolocft charging rato.
TIME/OIV and VARIABLE—Solocti
twoop rot# and oxtomol herliontal
Inpirl.
EXT HORIZ INPUT—Tormlnol for
occeptlng oxttrnol horfsontof sig-
nal.
STABIUrr—Poloi«ttoMolor for tol-
ling dc lorol of iwttp gonorotor.
INPUT—Ttrminol for occopling o«-
Hrnol triggoring tIgnoJ.
VERTICAL POSITION —PotiHont
iroco vortlcellv-
INPUT —Tfimlnal for occopling
wavofomii to bo dltployod on crt.
90LTS/DIV and VARIABLE —So-
locti vorlicol doflocKon foclor ond
callbralor signal
AC-OC-ONO—Solocit oilhor AC or
DC Input coupling. Tho CND poti-
tion connocit tho Vortical Ampliflor
to ground bvl doot not ground
tho input tignol.
Fig. 3-1. Funcdoni el tho Typo 3Z1A Otcllletcopo frani-^nol coniroli.
3-2

OperaHng InstrvcHeni —Type 321A
Fig. 3*3. Th« aKilleicop* ptelt Imtonlenaeut valrega variui Nma,
riiarahir laiving bath b> avaltaiaiar and atiiaar,
The Time Base ho$ 19 occuralely colibroted sweep rotes
ronging from .Spsec/div to 3sec/div. These colibroted
sweep rotes ore obtained when the VARIABLE (TIME/DIV)
control is fully clockwise in the CALIB position. The TIME/
DIV switch selects the colibroted sweep rotes and con be
rotated 360” since there ore no mechonicol stops. The VARI-
ABLE control permits you to vory the sweep role continuously
between .Sfisec/div and opproximotely 1.5sec/div. All
sweep rotes obtoined with the VARIABLE control in ony
position other thon fully clockwise ore uncolibroted.
Sweep Magnifier
Unmegnitiad Wovaterin
Fig. 3-3. Opararlan at tha «waap magnltiar.
Sweep Triggering
The oscilloscope display is formed by the repetitive sweep
of the spot across the oscilloscope screen. If the sweeps ore
allowed to occur ot rondom, or arote unrelated to the input
waveform, the displayed woveform will be traced out at o
different point on the screen with each sweep. This will
either cause the waveform to drift ocross the screen or to be
indistinguishable.
The sweep magnifier allows you to expand any two-
division portion of the displayed waveform to the full ten-
division width of the groticule. This is accomplished by first
using the HORIZONTAL POSITION control to move the por-
tion of the disploy you wish to expand to the center of the
graticule, then plocing the SX MAG switch in the "on "posi-
tion (pull out the red VARIABLE TIME/DIV knob; see Fig.
3'3). Any portion of the display mognified by the horizontal
sweep con then be observed by rotating the HORIZONTAL
POSITION control.
In mognified sweep operation, the sweep role indicated
by the position of the TIME/DIV switch must be divided by
5to obtoin the actual time required for the spot to move
one division. For example, if the TIME/DIV switch is set to
5MILLI SEC, the actuol lime per division is 5milliseconds
divided by 5, or 1millisecond per division. The actual time-
per-division must be used for all tirtie measurements.
External Horizontal Input
For special applications you can deflect the trace hori-
zontally with some externally derived waveform rather than
by means of the internol sweep sawtooth. This allows you
to use the oscilloscope to plot one function versus another.
To use the external horizontal input, connect the externally
derived waveform to the EXT HORIZ INPUT connector and
ploce the TIME/DIV switch in the EXT position. The hori-
zontal deflection factor is opproxlmaiely 1voil/division with
the 5XMAG on.
In most cases it is desiroble for repetitive woveforms to
appear stationary on the oscilloscope screen so that the
characteristics of the waveform con be examined in detail.
As anecessary condition lor this type of display, the start
of the sweep must beor adefinite, fixed-time relationship to
the observed woveform. This meons that eoch sweep must
storl at the same time, relative to some point on the observed
waveform. In the Type 321 A, this is accomplished by start-
ing or triggering the sweep with the displayed waveform, or
with another waveform bearing adefinite time relationship
to the disployed waveform.
The waveform used to start the horizontol sweep is called
a"triggering signal" (whether it is the waveform being ob-
served, or some other woveform). The following instructions
tell you how to select the triggering signal source.
Selecting the Triggering Source
In preporing the Type 321 AOscilloscope for triggered
operation of the sweep, it is first necessary to select the
triggering signal source v^ich will provide the best display
for the particulor application. The sweep can be triggered
by the disployed waveform, or by an externally derived
waveform. This selection is mode by the setting of the INT-
EXT switch (see Fig. 3-4). Each type of triggering hos certain
advantages for some applicotions.
Triggering from the disployed waveform is the method
most commonly used. The displayed waveform is selected
when the INT-EXT switch is in the INT position. Internal trig-
3-3

operating Instructlans —Type 321
A
gering is convenient since no external triggering connections
ore required. Satisfactory results are obloined In most appli-
cations.
To trigger the sweep from some external waveforrn, con-
nect the triggering waveform to the (TRIGGERING) INPUT
connector and place the INT-EXT switch in the EXT position.
(External triggering provides definite advonlages over in-
ternal triggering in certain cases.) With external triggering,
the triggering signal usuolly remains constant in amplitude
end shape, It is thereby possible to observe *he shaping ond
amplification of osignal in an external circuit without reset-
ting the oscilloscope triggering controls for each observotion.
Also, lime and phase relotionships between the woveforms at
different points in the circuit con be seen. If, for exomple,
the external triggering signol is derived from the waveform
at the input to acircuit, the time relationship ond phase of
the waveforms at each point in the circuit ore compared to
the input signol by the display presented on the oscilloscope
screen.
Selecting the Triggering Slope
The horirontol sweep can be triggered on either the rising
or foMirig portion of the triggering woveform. When the
SLOPE switch is in the +position, the sweep is triggered
on the rising portion of the triggering waveform; when the
SLOPE switch is in the —position, the sweep is triggered on
the falling portion of the woveform (see Fig. 3-5).
In mony opplicotions the triggering slope is not important
since triggering on either slope will provide adisplay suitable
to the opplicalion.
Selecting the Triggering Mode
Automatic Mode
Automatic triggering is obtained by rotating the (TRIG*
GERING) LEVEL control fully counterclockwise to the AUTO
position.
This mode allows triggering ot the average voltage point
of the applied waveform. Also, the sweep runs at approxi-
mately o50-cycle rote when no triggering signols ore ap-
plied; this produces areference trace or baseline on the
Kreen. Automatic triggering can be used with both internal
and external triggering signals, but for most woveforms
tis useful only for triggering at frequencies above 50 cycles.
Automatic triggering soves considerable time in observing
aseries of waveforms unce it is not necessory to reset the
triggering level for each observation. For t.Kis reason it is
the mode that is normolly used. Other modes ore generolly
used only for speciol applications, or where stable trigger-
ing is not attainable in the outomolic mode.
Fig. 3-4 The triggering (igtxil Is selected trem hura possible isvrces with the INT-tXT switch.
3-4

Operating Instructient —Type 321
A
Fig, 3-S. Eifi<ts on Iho OKilloicopo dliploy produ<od by +and —>otllng* ai rtio SLOPE and LEVEL <en(rol$.
3-5

Op«raNng InitnicNeni —Type 32) A
Ac Mode
Ac-mode triggering is obtained by setting the AC-DC
switch to the AC position. This mode provides stoble trig-
gering on vifluolly oil types of woveforms. As ogenerol
rule, however, the oc mode is unsotisfoctory for triggering
with low omplitude waveforms at frequencies below opproxi-
motely 15 cycles. This figure will vary depending upon the
amplitude and shape of the triggering woveform and should
not therefore be set as an absolute standard Triggering at
frequencies below IS cycles con be accomplished when
higher amplitude triggering signals ore used
In the ac mode, the triggering point depends on the
overage voltage level of the triggering signols. If the trig-
gering signols occur at rondom, the average voltoge level
will very causing the triggering point to vory olso. This shift
of the triggering point may be enough so that it is impossible
to mointoin ostable display. In such coses you should use
the dc mode.
Dc Mode
Dc mode triggering Is obtoined by setting the AC-DC
switch to the OC position. This mode of triggering is por-
ticularly useful in triggering from waveforms whidi ore not
odoptable to the ac mode, such os random pulse trains or
very low-frequency waveforms. Random pulse trains pose
aspecial problem in the oc mode since the random occur-
rence of the input woveforms causes the overage voltage
level to shift. This in turn may couse the triggering level to
shift to on unstable point. This problem is not encountered
in the dc mode since the triggering point is determined only
by instontaneous voltoges.
In the dc mode, when the triggering signol is obtained
from the Vertical Amplifier, varying the VERTICAL POSITION
control will change the triggering point. For this reoson,
you may find it necessary to readjust the LEVEL control when
you change the verltcol posilion of the trace. To eliminate
this effect, you con use the oc mode provided the triggering
signal is otherwise suitable for this mode of operotion. in
the dc mode, the dc level of the external triggering signals
will also effect the triggering point. Generolly, when the
triggering signal is small compared to its dc level, the oc
mode should be used.
How to Set the Triggering Level
In the oc ond dc triggering modes, the LEVEL control
determines the voltage level on the triggering woveform at
which the sweep is triggered. Using this conirol, the sweep
con be continuously triggered at any point on the woveform
so long os the slope of the waveform Is great enough to
provide stable triggering. In the dc mode, the sweep connol
be triggered wilh any degree of stobilily at the top of a
squorc wove, for example, because the time that the voltoge
remains constont is comporotively long. As oresult, the
sweep triggers at rondom pcir'ts olong the top of the squore
wove, producing consideroble trace jitter.
You con use the some metnod to set the LEVEL control for
either the oc or dc mode After selecting the triggering
slope, rotate the LEVEL control fully counterclockwise to the
AUTO position. Then rotate the LEVEL confrol clockwise
until the sweep no longer triggers Continue to rotate the
control in the clockwise direction until the sweep again trig-
gers and astable display is obtoined. Further rototion of the
control in the clockwise direction causes the sweep to trigger
at more positive points on the triggering waveform. In the
fully clockwise direction the trace will free run (Rg. 3-5),
FREE-RUNNING OPERATION
With the Type 321A, you con get operiodic, free-running
sweep, independent of any externol triggering or synchroniz-
ing signal, by rotating the LEVEL control fully clockwise to
the FREE RUN position. This permits you to observe the trace
without an input signal. This trace con then be used to posi-
lion the sweep or to establish avoltage reference line. The
difference between the traces produced in the AUTO posilion
and the FREE RUN position is the repetition rale. The repeti-
tion rate in the FREE RUN position is dependent upon the
setting of the timing switch, The repetition rote in the AUTO
position is fixed at opproximotely 50 cycles. At the faster
sweep rates, the troce in the AUTO position will appear to
be dim. In the FREE RUN position the trace intensity remoins
essentially constant for oil sweep rotes.
VERTICAL DEFLECTION SYSTEM
Input Coupling
Input signols to the Vertical Amplifier con be either ac- or
dc-covpied by placing the AC-DC-GND switch in the ap-
propriate AC or DC position. Dc coupling applies both the
oc ond dc components of the input signal to the vertical
amplifier circuit. This permits measurement of the dc voltoge
level os well os the amplitude of the oc component. It is
sometimes neither necessary nor desirable to display the dc
component, however, and in such coses as coupling should
be used. This is accomplished by setting the AC-DC-GNO
switch to AC. With oc coupling, ocapacitor is placed in
series with the input connector to block the dc component
while allowing the ac component to be displayed.
Placing the AC-DC-GND switch to the GND position
grounds the input circuit of the vertical amplifier to provide
a dc zero reference. In this posilion the switch internally dis-
connects, but does rtot ground, the applied signol to the
input connector. Thus, the GND position eliminates the usual
need for externally grounding the (Vertical Amplifier) INPUT
conr>ccior of the Type 321 Aor the probe lip to estoblish a
ground reference.
Deflection Factor
The electricol waveform to be observed is applied to the
(Vertical Amplifier) INPUT connector. The waveform is then
applied through the vertical-deflection system to cause the
spot to be deflected verticolly to trace out Ihe waveform on
the screen of the ert. The VOLTS/OIV switch controls the
vertical deflection foctor in accurolely calibrated steps. The
VARIABLE control provides uncolibrated variable deflection
factors between the fixed steps of the VOLTS/DIV switch.
The VARIABLE conirol has 360* rotation range and adetent
position when the control is set to CALIB.
3-6

Operating Instructions —Type 32 1
A
NOTE
To moke the deflection factor equal to that indi-
coted by the VOITS/DIV switch, set the VARIABLE
control to the CALIB detent position.
Dc Balance Adjustment
The need for adjustment of the DC BAL control is irtdi-
coled byoverticol shift in the position of the trace os the
VARIABLE (VOLTS/OIVj control is rotated, This adjustment
should be mode as follows;
1. Set the AC-OC-GND switch to GND.
7.Set the oscilloscope controls (or ofree-running trace.
3. Rotate the VARIABLE (VOLTS/DIV) control back and forth,
and adjust the DC BAL control simultaneously until the
trace position is no longer effected by rotation of the
VARIABLE control.
Input Signal Connections
Certain precautions must be observed when you are con-
necting the oscilloscope to on input signol source. This is
to insure that accurate information is obtained from the
oscilloscope display. This is particularly true when you
are observing low-level signals, or woveforms containing
high- or extremely low-frequency components. For applica-
tions where you are observing low-level signols, shielded
cables should be used whenever possible, with the shield
connected to the chassis of both the oscilloscope and the
signal source. Unshielded input leods are generally unsatis-
factory due to their tendency to pick up story signals which
produce erroneous oscilloscope displays. Regardless of the
type of input used, the leads should be kept as short os
possible.
Distortion of the input waveform may result if;
1.Very low-frequency input sigriols ore oc-coupled to the
oscilloscope.
2. High-frequency waveforms are not properly terminated.
3. The input waveform contains high-frequency components
which exceed the bondpass of the oscilloscope.
You must be aware of the limitations of the instrument.
In analyzing the displayed waveform, you must consider
the loading effect of the oscilloscope on the input signal
source. In most coses this loading effect is negligible; how-
ever, In some oppllcotions loading caused by the oscilloscope
moy moterially alter the results obtained. In such cases you
moy wish to reduce the amount of looding to onegligible
omount through the use of oprobe.
Use of Probes
Occosionolly connecting the input of an oscilloscope to
asignal source loads the source sufficiently to adversely
effect both the operation of the source and the waveform
disployed on the oscilloscope. In such coses an attenuator
probe may be used to decrease both the capacitive end resis-
tive loading caused by the oscilloscope to anegligible value.
In addition to providing isolation of the oscilloscope from
the signal source, an otlenuotor probe also dccreoses the
amplitude of the displayed waveform by the ottenuotion
foctor of the probe. Use of the probe allows you to increase
the vertical-deflection factors of the oscilloscope to observe
large-amplitude signals beyond the normal limits of the
oscilloscope. Signol amplitudes, however, must be limited to
the moximum allowable value of the probe used. When
making omplitude measurements with on attenuator probe,
be sure to multiply the observed omplitude by the ottenuo-
lion of the probe.
If the waveform being disployed hos rapidly rising or
falling voltages, it is generally necessory to clip the probe
ground lead to the chassis of the equipment being tested.
Select aground point near the point of measurement, as
shown in Fig. 3-6.
^lobt lip conn»ct*d to signal leurc*
grpundtoed tannoctod to thesih
Squipmtnr iMing chackad
fig. )-6. Cennvtting opiob* >« th* input signal tnutts
Before using aprobe you must check (and adjust If neces-
sary) the eompensotion of the probe to prevent distortion of
the applied woveform. The probe is compensated by adjust-
ing the control located in the body of the probe. Adjuslmcnl
of the probe compensates for variations in input copodtonce
from one instrument to onother. To insure the occurocy of
pulse ond transient measurements, this odjustmeni should be
checked frequently.
To adjust the probe compensation, set the VOLTS/OIV con-
trol to the .01 position and the LEVEL control to the AUTO
position. Set the SLOPE switch to 4ond the INT-EXT switch
to INT. Connect the probe tip to the CAL OUT 500 MV con-
nector. Set the TIME/DIV switch to .5 MILLI SEC ond adjust
the probe to obtain flat tops on the displayed square wove-
form (see Fig. 3-7.)
3-7

Operating Instructions —Typ« 321
A
Voltage Measurements
The Type 321 AOscilloscope can be used to measure the
voltage of the input woveform by using the calibroted ver-
ticol deflection foctors of the oscilloscope. The method
used for oil voltage meosurements is basically the some
although the actual techniques vory somewhot depending on
the types of voltage measurements, i.c., ac-component volt-
oge measuromenls, or instamoneous voltage measurements
w'lh respect to some reference potentioi. Mony waveforms
contain both ac and dc voltage components, ond it is often
necessary to measure one or both of these components.
When making voltage tneosuremenis, you should display
the waveform over os large averticol portion of the screen
os possible for moximum occurocy. Also, it is tmportont that
you do not include the width of the troce in your measure-
menfi. You should consistonl'y make all meosurements from
one side of the trace. If the bottom side of the trace is used
for ore reading, it should be used for all succeeding read-
ings. The VARIABLE (VOLTS/OIV} control must be in the
CALI8 detent position,
Ac Component Voltage Measurements
To measure the oc component of owovefoim, the AC-DC-
GND switch should be set to the AC position In this position
only the oc components O'^ the input waveform are disployed
on the osc'l'oscope screen. However, v/hen the oc component
of the input waveform is very low in frequency, i* will be
necessary for you to moke voltogo measurements with the
AC-DC-GND switch in the OC position.
To moke apeak-fo-peok voltoge meosurement on the ac
comporient of a waveform, perform the following steps |$ee
Fig. 3-8).
1. With the aid of the grollcule, meosure the vertical dis*
tance in divisions from the positive peak to the negative
peak.
2. Multiply the setting of the VOLTS/OIV control by the dis-
tance measured to obtain the indicated voltage.
3. Multiply the indicoled voltoge by the attenuation factor
of the probe you ore using to obtain the true peak-lo-peak
voltage.
As on exomple of this method, assume thot using the
P6006 Probe and odeflection factor of 1volt per division,
you measure overtical distonce between peaks of 4divisions.
In this cose, then, 4divisions multiplied by 1volt per divi-
sion gives you on indicated voltage of 4volts peok-to-peok.
The indicated voltage multiplied by the probe's attenuation
factor of 10 then gives you the true peak-to-peok amplitude
of 40 volts.
When sinusoidal waveforms are measured, the peak-to-
peok voltage obtolned con be converted to peak, rms. or
average voltage through use of standard conversion factors,
InsLonTaneous Voltage Measurements
The method used to measure instantaneous volloges is
virtuoily identicol to the method described previously for
the measurement of rhe oc components of owoveform. How-
ever, For instonlaneous voltoge measurements the AC-DC-
GND switch must be placed in the DC position. Also, since
inslantar^eous volloges ore meosured with respect to some
potentiol [usually ground), areference lino must be
estoblished on the oscilloscope screen which corresponds to
that potentiol. If, for exomple, voltage meosuremer'ts ore to
be made with respect to -t'100 volts, ‘he reference line would
correspond to -<-100 volts. In the following procedure a
method is presented for establishing this reference line ol
ground, since measurements with respect to ground are the
Incorrect Adjuitod Cerroctly IrKerreet
P6006 Prebo—Meld prebe barrel ond
leecen leckine rleeve teverol tvmc. Keld
prebe bote while sduicHng prebe barrel
ter llaf-tep sguore wovet. Held probe
barrel ortd carefully Hghlen lecliine
ileeee
Fig. 3-7. The prebe i« ad|u(ted te ebioin en urtdlttered preieniotlen el ihe calibrator iqeeiewcne.

Operating Instructions —Type 32) A
Fig. 3-8. MMituring lh« p«oli-r»-piob ac yolleg* »f an opplivd wevvfotin.
most common type. The some general method moy be used
to measure voltoge with respect to any other potential, how-
ever, so lortg os thot potentiol is used to establish the ref-
erence line.
To obtain an intontoneous voltage meosurement with res-
pect to ground, or some other voltage, perform the following
steps (see Fig. 3-9|.
1. To estoblish aground reference line, set the AC-DC-
GND switch to GND. Or, to establish oreference line
which represents ovoltage other than ground, touch the
probe tip to the voltoge and leave the AC-OC-GND
switch at DC. Then adjust the oscilloscope controls to
obtoln ofree-running sweep. Vertically position the trace
to aconvenient point on the oscilloscope screen. This
point will depend on the polarity ond omplilude of the in-
put signal, but should always be chosen so that the trace
lies along one of the mojor divisions of the graticule.
The graticule division corresponding to the position of
the trace is the voltoge reference line ond all voltage
meosurements must be mode with respect to this line.
(Do not adjust the VERTICAL POSITION control ofter the
reference line has been established.)
2. If ground reference wos estobllshed, set the AC-DC-GND
switch to DC; if areference line other thon ground was
established, remove the probe tip from this voltoge ond
connect it to the signol source. Adjust the LEVEL control
for 0stable disploy.
Fr«-«(rebllthad
tin*
tuiualiy gieund)
Vartlcsl Dailtctlan
Fram Raiaranca Una
Inilantonaeut
Veltega Wxh
Raiparl Ta
Ralaraftca Valtoga
Praba Attanuotlan Factor
Ftg. 3-9. Maacuring iha inrtanranaavi valtaga wHh raepaef ta ground (at taina athar talartrHa voOogat.
3-9

Operotin0Instruction! Typ« 321
A
3. Mcosure the vertical distonce in divisions From the desired
point on the wovolorrr to the voltoge reference iine.
<4. t^ultiply the sotting of the VOLTS/DIV control by the dis-
tance measured to obtoin the indicated voltoge.
5. Multiply the indicated voltoge by the attenuation factor
of the probe you ore using to obtain the actual voltoge
with respect to ground (or other reference voltoge].
As on example of this method, ossumo you ore usittg the
PdOOd Probe and odeflection foctor of 03volt per division.
Alter setting the voltage reference line oi the second from
bottom division of the graticule, you measure odistonce of
3divisions to the point you wish to check. In this case,
3divisions multiplied by 0.2 volt per division gives you on
indicoted 0.6 veil. Since the voltage point is above the
voltage reference line the polarity is indicated to be posi-
tive. The indico'ed voltage multiplied by the probe attenua-
tion foctor of 10 then gives you the actuol voltoge of +6
volts.
Time Measurements
The colibrated sweep of the Type 321 AOscilloscope causes
any horizontal distonce on the screen to represent odefinite
known interval of time. Using this feature you con occurately
measure the time lapse between two events displayed on
the oscilloscope screen. One method which produces suf-
ficient occurocy for most opplicoiions is os follows (see
Fig. 3.10).
1. Meosure the horizontal distance between the two dis-
ployed events whose time intervol you wish to find.
2. Multiply the distonce measured by the setting of the
TIME/DIV control to obtain the opporent time interval.
(The VARIABLE TIME/OIV control must in the CALIB posi-
tion.)
NOTE
Divide the apparent time interval by 5 if the mag.
nifier bon.
rig. }-10. Manuring th« inlarvol batwtan avanrs dl>glsrae an >ha a*<lllaMa^ scraan.
3-TO