Tektronix 321 A User manual

INSTRUCTIC>N
MANUAL
TYPE
321A
OSCILLOSCOPE
T ek tronix, Inc.
S. W. Millikan Way • P. 0 . Bo x 500 • B eaver t on , Or e gon 97005 • Phone [phone] e Cab l es : Tektronix
070 - 425
564

AU Tektto. i*lt!iflijilllllib
GQGinst defective . •• ._,.
ship for one year.
·.
Any que stions with respect to the wor-
raaty mentioned above should be token up
with your Tektronix Field Engineer.
Tektronix repoir
and replacement-port
semce is geared directly to the field, there -
fore all requests for repairs and reploce-
JIIent ports. should be directed to the Te k-
tfonix Field Offic:e oc Representa
ti ve in your
area . Th is procedure will assure you the
fclstett po ssible servic6. Please inctude th_e
iftsttument Type and Serial number with all
....,ests for ports or service.
• Specifications and pr ice change priv-
""-' reserved.
.,. :Copyright © 1964 by Tektroni ~, Inc .,
. ~erton, Oregc)n. Printed in the United
.,. '$ililes of America. All rights reserved.
Oottents of th is publication may n ot be re-
.. ~uced in o n~ form without permission
he copyright owner.

Type 321A

Type 321A
SECTION I
CHARACTERISTICS
lntrodudion
The Tektronix Type 321A is a high-performance, dc -to-6
me, transistorized oscilloscope. Its light weight, small size
and ability to operate from o variety of powe r sources make
it a versatile field and laboratory instrument. The oscillo-
scope con operate from its internally-contai ned rechargeable
battery pock, on external de source or from o 115/230-vo lt
50-800 cycle ac line. Regulated power supplies in the instru-
ment, accur
ate calibration, and precise linearity assure exa ct
time
and amplitude measurements despite normal voltage-
source and powe r- supply-lo ad changes that occur under
odual operating conditions.
Operating temperature range derived from tests in dicates
optimum performance
and reliability on its self- conta i ned
batteries from o· to + 40° c ot altitudes up to 15,000 feet.
Temperature
range without batteries when opera ting from on
external source is - 15 • C to +55 • C. Non-operating tem-
perature range is -55" C to +7 5" C without batteries
and -40• C to + 60" C with batteries at alt itu des to
50 , 000 feet.
For the operator's convenience, a front-panel battery lighl
in dicates when the internal batteries o re low. If external de
or ac operation is being used instead of the batteries, the
light turns on if the external volt ag e source drops too low
for
proper power supply regulation.
A 4-position
power switch on the front panel permits
convenient selection
of charging rote and /or power source.
Vertical Deflection System
Bandpass-De to at least 6 me (3-db down) using de cou-
pl in g; using oc coupling, low-frequency 3-db down po in l
is 2cps typical from a 1-kc reference.
Sensitivity-0.01
v/div to 20 v/div in 11 calibrated steps;
occurocy is within 3"/o of front- pane l markings. Con-
tinuously variable from 0. 01 v/div to abou t 50 v/div
uncolibroted.
Input lmpedanc
e-35 pf nominal paralleled by 1 megohm
(:.t 1 "/o), 8.2 pf nominal paralleled by 10 megohms
(±2%1 when using the P6006 lO X Probe.
Maximum Allowable Input Voltage
Roting-600 volts com-
bined
de and peak oc ; 600 volts (not 1200 volt s) peak-to-
peak oc .
Triggering
Type-Automatic, or amplitude-level selecti on using pre -
set stability.
Modo-Ac -c oupled or De-coupled.
Slope-P lus, from rising slope of triggering waveform, or
minus from negative slope of triggering waveform.
Source-Internal from vertical signal, or external from
triggering signal.
Signal Requirements-Internal: 0.2 majo r division vertical
deflection at 1kc increasing to 1 major division at 6 me.
External: 1 volt peok-to-peak at l kc increasing to 3 volts
peak -to-peak at 6 me. Nominal input impedance: 5 pf
paralle l ed by 100 kilohms (± 20%).
Sweep
Type-Miller Integrator.
Sweep Rotes-0 .5JLsec/div to O.S sei:/div in 19 c alibrated
steps. Accurate 5X sweep magnifier extends calibrat ed
range to 0.1 p.sec/div. Calibrated sweep-rote accuracy
is :
t: 3"/o. Sweep time adjustable between steps and to
~ 1.5 sec/div uncolibrated.
External Ho rizontal Input
Bandpas s- De to at least 1 me (3-db down).
Deflection Foetor-! vfdv + 10"/o with 5X magnifier an .
Input lmpedanc&-30 pf typical paralleled by 100 kilohms
1±
5% ).
Amplitude Calibrator
Square Wove-Frequency about 2 kc.
Amplitud e-500 mv peak - to -pe ak . Also 40 mv peok-to·
peak internally coupled in CAL4 DIV position of VOLTS/
DIV switch. Peak-to- peok amplitude accu racy is ± 3% .
Cathode-Ray Tube
Typ e-Speci al Tektronix-manufactured 13211. 3" flat-face,
post-deflection
acce le rator . l ow healer power .
Accelerating
Potcntiol-4 kv.
Z-Axis Modulation-External terminal permits
RC coupling
to crt grid.
Unb lonking -Defle ction unblanking.
Phosphor-Type
P31 normally furnished; PI, P2 , P7, and
Pl l phosphors optional. Other phosphors furnished on
special
order .
Graticule
Illumination-Variable edge lighting when operating from
ac line.
Display Area -Marked In 6-vertical and 10-horizontol 1
/4"
divisions.
Power Requirements
Source-Operates from I0 size D flashlight cells, or 10
size D rechargeable cells (approximately 3 hours using
2.5
ampere -hour cells; approximately 5 hours using 4
1-1

Choraderistics - Typ e 321A
ampere-hour cells), or 11.5 to 35 volts de (aircraft, auto ,
boot, etc.),
or 103.5 to 126.5 volts or 207 to 253 volts,
rms, 50 to 800 cycles, single-phose oc.
Power Consumption-Approximately 700 mo from internal
batteries
or eldernol de source; 20 watts nominal at
115 -v olt ac line.
Temperalure Prot ection- Thermal cutout switch interrupts
power
if amb ient temperature exceeds 13 1" F (55" C).
Built- in battery charger is standard equipment.
Environmental Capabilities
Vibration (operating)-0.025" peak-to-peale, 10 to 55 to
10 cps in 1 minute sweeps (4. G's) for 15 minutes on
each axis.. Three-minute vibration at resonance or
55cps on each axis.
Shock (operot ing}-20 G's, lj
2 sine, 11-msec duration.
1-2
Two shocks each direction along each of the three
ma jor a xis: bollom, lop, left side, right side, front
and rear.
To t al of 12 shocks.
Shock lnon-operaling)-60 G's, 1f
2 sine,
11 -msec duro-
lion.
One shock each direction al ong e ach of the three
major axis; total of 6 shocks.
Hum idity (non-o perating)-Mee ts Mi i- Std-2028, method
106A (ex cept freezing and vibrat ion) through 5 cycles
(120 ho urs).
Transit (non- ope roting}-Meets Notional Sofe Transit lest
when factory packaged . Vibration for one hour at
slightly greater than one G. Eight een-inch drop in any
orientation.
Mechanical Spe(ificotions
Construct ion-A luminum alloy chassis and cabinet.
Finish -Anodized panel, blue vinyl-finish cabine t.
Dimensions-Slf," high, 53//' wide, 16" deep overall.
ACCESSORIES
Information on accessories fo r use with this instrument is
included at the r ear of the mechanical ports list.

SECTION 2
PRELIMINARY INSTRUCTIONS
Power Requirements
The regulated power supplies in the Type 321 A w ill operote
form 115-v or
23 0-v rms oc line, from on external de so urce
(11.5 to 35 volts),
or from o ''battery pock '' consisting of
either 10 size D flashlight cells or 10 size D recharge ab le
cells.
Fuse Data
Use only the recommended f uses in the Type 321A Oscil-
loscope. The upper fu se , F 621 ( se e Fig. 2-1 ), is a 1.5-amp
3AG Fast-Blo; th e lower fuse , F601 , is a . 25 -omp 3AG Fast -
Bio.
Neither fuse needs to be changed if the oscilloscope
is converted from one line voltage to the other
(115 v and
230v).
fig . 2- 1. location of fu ns and Charger twitch lleft-sl de v ie w) .
Ac Operation
Unless togged otherwise, your instrument is connected ot
the factory lor operation ot 103 .5 to 126 .5 volts, 50 to 800
cycles oc ( 11 5 volts nominal). How ev er, provisions ore mode
for easy conversion to operate at 207 to
253 volts, 50 to
800 cycles (230 volts nominal). The power transformer T601
is provided with split input windings which ore normally
connected in parallel for 115-volt operation, but which can
be connected in series for 230 -vo lt operation.
The primary windings ore marked l, 2, 3, and 4. Terminols
1 and 3 ore connected to one winding and terminals 2 and 4
ore connected to the second winding. The oc inp ut leads ore
connected to terminals 1 and 4 for both 115-volt one 230-
®
volt operation, so these connections do not hove to be
chang ed when converting from one line voltage to the other.
When wired for 115-volt operation, te
rm inals 1 and 2 are
joined by o bare bus wire, ond termina ls 3 and 4 ore simi-
larly joined, as shown in Fig. 2-2 1o). To convert to 230-
volt operation, remove the bore bus wires between these
termina ls and substitute a single connecting wire between
terminals 2 and 3,
as shown in Fig. 2-2(b).
To turn on the Type 321A when the power cord is con-
nected to the oscilloscope power connect or and to t he oc
voltage so urce, se t the POWER switch to EXT ON. To turn
off the oscilloscope, set the POWER switch .to TR IC KLE . The
TRICKLE position con be regarded as the normal " off " posi-
tion for t he instrument.
To 115 -v AC
(al
To 230-v AC
F lg . 2-2 . ( al Transform er connection for operation from 1 03 .5-
126 .5 vo lt oc line ; lb) tonneclions fo r operation from 207-253
volt ac line .
As lo ng as the oc power cord is connected to the oc line,
power is being applied to the power transformer T 60 1, ac-
rectifier c ir cuit, and groticule light s for oil positions of the
POWER switch. Appli cation of power to these circuit is re-
quired to provide battery-charger operation for th e internal
batteries; t
he groticule lights provide visual indication that
these circuits ore ··on". Power to the battery charger itself is
controlled by o Charger switch (see Fig. 2·1). If the switch
2-1

Preliminary Instruction s- Type 321 A
1s set to LOW or HIGH, the ac rectifier is connected to the
battery charger circuit which, in turn, provides charging cur-
rent to the internal rechargeable batteries.
NOTE
If dry cells ore used inst ead of rechargeable bat-
teries, then the Charger switch must be set to DR Y
CELLS to disconnect the charger circuit. For further
information about battery operation, r efer to the
topics tilled "Battery Operation" and "Ba tt ery
Charger" appearing in this sect io n of the manual.
If the Type 321 A is being operated exclusively from the
oc line and the internal batteries ore removed, the Charger
switch can remain in the DRY CELLS position to disconnect
the charger ci rcuit. If you prefer to completely turn off
oil power to t he Type 321 A, set the POWER sw itch to
TRICKlE and either disconnect the power cord from the
ac li
ne or turn off the power at o wall switch (or equiv-
alent).
Batt ery Operation
Operation from the internal battery source can be accom-
plished by using :
1. Ten size D flashlight cells (approximately 1
/1-hour con-
tinuous operation, more with intermittent operation), or
2. Ten si ze D Alkaline cells such as Eveready E95 , Bu rgess
Al-2, or Mallory MN-1300 (about 21
/2 hours
co ntinuous
operation), or
3. Ten size D ni ckel -cadmium rechargeable cells (up to
about 5 hours continuous operation, depending on the
type
used).
The nickel-cadmium cells ore the most practical type where
considerable battery operation
is planned.
To install the cells, ftrst open the battery cover as ill us -
trated in Fig. 2-3. Next, install the batteries by following
the procedure gi
ven in Fig . 2-4.
CA U TIO N
Be su re to observe cell po lari ty i ndi cated on the
battery cover.
To turn on the Type 321A when operating from the internal
batteries,
set the POWERswitch to BATT ON. To turn off the
oscilloscope, set the POWER switch to one of the OFF posi-
tions-FULL or TRICKLE. These OFF positi ons disconnect
t
he batteries from the oscilloscope load (1 0-volt regulated
supply)
so there is no battery drain. To charge the recharge-
able batteries, refer to the next topic titled "Battery Charger".
Fig. 2·3 • .Removing lhe ba ii••Y cover from the Typ• 321 A Oscllloltope .
2-2

Preliminary Instructions- Type 321 A
Fig. 2-4 . Proced11re for ln stolllng the bo »eries .
Battery Charger
As mentioned previously, the battery charger is connected
to the internal batteries as long as the oc power cord is
connected to
an ac power source and the Charger switch
(see Fig. 2-1) is set to HIGH or LOW. No charging occurs if
the Charger switch is set to DRY CELLS .
Table
2-1 summarizes the charging currents that con be
obtained by using various line voltages in combination with
various settings
of the POWER and Charger switches. Th e
table shows the Type 321A wired for 115-volt nominal line
operation. If the oscillosco pe is wired for 230-vo lt nominal
line
operation, the charging currents will still be the some
but the ac li ne voltages will be twice the amount shown in
the table.
Use Table 2-1
as on aid in determining the proper posi·
lion for the POWER and Charger switches for the particular
brand or type of rechargeable batteries being used in the
Type 321A. After setting the switches to th eir 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 a rating of at least I ampere and
equ i pped with on rms-reoding oc voltmeter con be used to
set the line voltage.
When using rechargeable batteries, sixteen hours of
charg ing at the full rated charging current recommended
by the manufacturers should be adequate to fully charge
the batteries. Excess charging may damage the batter ies.
One method for determining charge conditions of the bat -
teries is to set the POWER switch to BAIT ON and then
measure the voltage across the battery terminals ( sec Fig.
2-
4) . A read ing higher than 13 volts in dicates that the
ba tteries are fully charged. A reading lower than 13 volts
indic
ates that more cha rging time is required.
As mentioned previously, if dry cells ore installed in the
battery holder and the Type 321A is being operated from
the
ac line, the Charger switch must be set to the DRY CELLS
position. This position disconnects the charging circuit from
the batteries.
TABLE 2-1
Charging Currents
PO WER • Charger Aproximote Charging
Swit ch Switch Current in Ma
Position Po sitio!:'... ]_0~.5 - " ... ) - ~(~~ ;~ (~ .- ~ ·.·. ;:, 12 ~ ~ 1 126.5 v
- Low ······ · 2o · ·········· 2:.~ ··r-· v 31 · 33
EXT ON - - .. ······----·-··-- -- ·
-- -- · ·- ·- · - [6~ r----· ;f. - ;: ' --1§ --·- ~~ L - ---·--- !~ ····-
TRICKLE - - ·· -········- -
HIGH 34 37 1 41 4A 48
~~~ -~ ~~~ --- ·.·.·.· .. -~ J - ~ ~- -: r ;~ -=- ~~ - -- - ·---·- ~~ ~
"The BATl ON po•llion is not Inclu ded in the tab le becouae the
T ype 321 A should not be operored from the oc tine ond lho
bollories or the some limo. R eosona Bollory drain oxc::eod• chorg ·
lng role .
2-3

Prelim inary Instructions- Typ e 321A
De Operation
Operation from on external de source is ocompli1hed by
connecting the special pigtail-type de power cord in the
proper manner.
Fo r 11.5 - to 20-volt operation, t he block
1+1 and white 1-) leads ore connected to the voltage
source ; for 20- to 35 -volr operation, the green 1+1 and wh ite
1-·) lea ds or e connected to 1hc voltage source. When the
connect
io ns to the external de voltage source arc properly
mode, the external de source
is floating with res pect to the
Type
321A chassis. Up to 600 volts difference is permissi-
ble, if necessary.
To turn on the Type 321 A, set the POWER swi t ch to E XT
ON . To turn off the oscilloscope, set th e POWER switch to
one of t he OFF pos itio ns - TRICKLE or FULL.
When operating from the external de source, the ac line
cord
shou ld be disconnected. Tha t is, only one of th e exter-
nal
sources sh ould be used rather than bo th at the some time.
2-4
NO TE
Th e internal battery cha r ge r circuit is d is connected
during external de operation . Ther efo re, ext ernal
batteri es ( if used as the de sourcel cannot be
ch arged by connecting the line cord to the oc line.
Also, on external de source
cannot be used to
ch ar ge the internal batter i es since the POWER
switch does not electrically connect the twa
sources t ogether.
LOW BATTERIES Ught
The LOW BATT ERI ES light tu rns on when the following
conditions exist:
1. Tho POWER switch is set to BA TI ON and the internal
batteries drop to
11.5 v ( :!.:. 0.2 v) or lower.
2. T he POWER swi t ch is set to EXT ON and the external
source voltage is low enough to ca use the Type 321A un-
regulated voltage to drop to about 11.5 v or lower.

SECTION 3
OPERATING INSTRUCTIONS
General Information
The Type 321A Oscilloscope is an extremely versatile in-
strument, ad aptable to a great number of app li cations. How -
ever, to make full
use of the instrument, it is neces .sary that·
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 ore
familiar with other Tektron ix oscilloscopes, you should have
very litt le difficulty in understanding the operation of the
Type
321 A. The function of many controls is the same as
the function of corr~sponding controls on other Tektronix
instruments. A front-panel view of the Type 321 A is shown
in Fig. 3-1.
Intensity Control
The INTENSITY control is used to adjust the trace bright-
ness. This permits adjustment of trace in tens ity to suit the
ambient
light conditions and changes in intensity caused
by changes in the sweep triggering rote (sweep duty cycle).
Clockwise rotation increases the intensity and counterclock-·
w ise rotation decreases t he intensity.
Focu s and Astigmatism Controls
The FOCUS and ASTIGMATISM controls operate in con-
junction with each other to allow you to obtoin o sharp.
clearly defined spot or trace. To odiust these controls:
1. Adjust the IN T ENSITY control for the most pleasing level.
2. Set the ASTIGMATISM control to midscale.
3. Adiust the FOCUS control for sharpest detail.
4. Adjust the ASTIGMATISM control as necessary for best
overall focus.
Groticule Illumination Control
The graticule used with the Type 321 A is accurately
marked with 10 horizontal and 6 vertical divisions, with 0.2-
division markers on the centerlines. These groticule markings
allow you to obtain time and voltage measurements from
the oscilloscope screen.
Graticule illumination is adjusted by the SCALE ILLUM
control, located just to the right
of the oscilloscope screen.
Rota ting the control clockwise increases the brightness of the
graticule markings and counterclockwise rotation decreases.
the brightness.
NOTE
The gratic ule is I llu mina ted only when ope ra ting
from on oc line . This permits longer oper at ion
when on batter ies.
Positioning Controls
Two controls are used with the Type 321 A Oscilloscope
to position the trace or spot on the screen.
The HORIZONTAL PO SITION control moves t he trace to
the right when it is rotated clockwise and to the left when it
is rotated counterclockwise. This control has o positioning
range
of approximately 15 divisions with the sweep magnifier
off, ond approximately
75 divisions with the sweep magnifier
on.
The HORIZONTAL POSITION control is a combination
coarse/vernier type
of control. Built-in blaclda sh between
its
two sections permits 30° of vernier adjustment for o given
coarse setting.
IF a 30° range is exceeded, the coarse ad-
justment tokes over to provide fast positioning of the trace.
The VERTIC AL POSITION control has sufficient range to
position the trace completely
off the top or bottom of the
screen, or to any intermediate point. The trace moves up
when the control is rotated clockwise and down with the
counterclockwise rotation.
Inten si ty Modulation
The crt display of the Type 321 A Oscilloscope con be in-
tensity modulated by on external signal to display additional
information. This is accomplished by disconnecting the
grounding
bar from the CRT GRID connector at the rear of
the instrument and connecting the external signal to this
terminal. A negative signal of approximately 30 volts peak
is required to cut off t he beam from maximum intensity, less
with lower intensity levels. Negat ive-going signals as low as
5 volts peak will accomplish intensity modulation.
HORIZONTAl DEFLECTION SYSTEM
Horizontal Sweep
The usual oscilloscope display is a graphical presentation
of instantaneous voltage versus time. Voltage is represented
by vertical deflection of the trace and time is represented
by horizontal deflection. To obtain o useful display, the spot
formed
by the electron beam is deflected horizontally at a
known rote,
so that any horizontal distance on the screen
represents a definite known period of time. The trace formed
by the deflection of the spot across the screen is known as
the horizontal sweep. Since the horizontal def lection of the
spot bears o definite relationship to ti me , and provides the
means for making ti me measurements from the screen, the
horizontal sweep is also known as the time bose. (See Fig.
3-2).
The rote at which t ho spot is deflected across the screen
is accurately controlled by the setting of t he TIME/DIV con-
trol. Tho setting of the TIME/DIY control determines the
sweep rote, and
thus the number of cycles displayed on the
crt screen . The control is set to display the portion of the
waveform you wish
to observe.
3-1

Operating lnstrudl ons -Type 321A
CRT CONTROLS
FOCUS -Controls aharpneu of
spot or trace .
ASTIGMATISM-·lhed In conjunc•
li
on with FOCUS to obta in overa ll
focus.
VERTICAL CONTROLS
VERTICAL POSITI ON
tra ce vertically.
AC-OC - GND-Sele cls tither AC or -- -+~• .J
OC In put coupling. Th o GND posl·
tion connectt the Vertic al Amplifi er
to ground b111 does not gro un d
the i
nput sig rta l.
90LTS /D IV a nd VARIABlE -Se-
le ct s vertical defle<lion fa<lor and
cali brato r signa l.
INPUT -Terminal
for accepting
w avefo rms to be disp laye d on crt.
CAL OUT 500 MY-Term i nal pro-
vides 500 -mv sq11are wave for
com pe ns ating probe .
DC BAL-I'otent l ometer for se tting
de balance of Vertical Amplifier.
INTENSITY-Cont ro ls brigh tneu of
trace .
SCAlE
llLUM--Adjuate br lgh tneu
of gratfcule marking s ! when oper-
at ing from AC Hnel .
HORIZONTAL POSITION--Coars e-
vernier type of control that posf·
lions t race ho rlaon ta lly.
POWER
-Switch tum a regula t ed
10 -~ olt power on and off . Al so,
selects charging rate .
EXT HORIZ IN PUT -Terminal for
accepting ex ternal horizontal sig-
nal.
CONTROLS
S LOPE--Oe ter min es whether sweep
is tri ggered on + or - sl ope of
trig
ge ring signa l.
AC-OC-Sel e ds AC or DC coupling
for tri gger ing si gna l.
STA 8tl tT Y-Potentlo met er for s et ·
ling de level of swee p genef'Citor.
INPUT- Term
inal for ac ce pting ex-
t erna l t riggering signal.
Fig. 3-1. fun cti on s of the Type 321 A Oscilloscope fron t -pane l c ontro ls.
3-2

l
I- f-
1 .-- 1 .--
J
rP
...
w w
r r
V oltage
~
f-1 f-1
Time --------..
Fig. 3- 2. T he o sd llo ~e ope plots Inst an tan eous voltoge v ert us t ime ,
thereby se rvi ng bo th as o voltmet er o nd a timer.
The Time Ba~e has 19 accurately calibrated sweep rate s
ranging from .5 JJ.Sec/div to .5 sec/div. These calibrated
sweep ra
tes ore obtained when the VA R IA B LE (TIME/DIY)
con trol is fully clockwise in the CA LI S position. The TIME/
DIY switch selects t
he calibrated swee p rates and can be
rotated 360 •
since there are no mechanical stops. The VA RI ·
ABLE control permits you to vary the sweep rote continuously
between
.5 11-S ec/div and approximately 1.5 sec/div. All
sweep rates obtained with the VA RIABLE control in any
position other than fully clockwise ore uncalibroted.
Swe ep Magnifier
The swee p magnifier allows you to expand any two ·
division portion of the displayed waveform to the full ten·
division width of the grolicule. This is accomplished by first
us ing the HORIZONT AL POS ITI ON control to move the par·
lion of the display you wish to expand to the center of the
graticule, then placing
the 5X MAG switch in the ··on" posi-
tion (pull out the red VARIABLE TIME/DIY knob; see Fig.
3-3). Any portion of the display magnified by the horizontal
sweep con then be observed by rotating the
HORIZONTAl
POSITION control.
In magnified sweep operation, the sweep rote in dicated
by the position of the TIME/DIY switch must be div ided by
5 to obtain the actual ti me required for the spot to move
one division.
For example, if the TIME /DIY switch is set to
5 MILLI SEC, the actual time per division is 5 milliseconds
divided by 5, or 1 mi lli second per div is io n. The actual time-
per-division mus t be used for all time measurements.
External Horizontal Input
For special applications you can deflect the trace hori-
zontally with
some externa lly derived waveform rather than
by means
of the internal sweep sawtooth. This allows you
to
use the oscilloscope to plo t one function versus another.
To
use the external horizontal input, connect the externally
derived waveform to the
EXT HORIZ INPUT connector and
place the TIME/DIY switch in the EXT position. The hori-
zontal deflection foetor is approximately 1 volt /di vision with
the 5X MAG on.
Op er ating In struction s- Type 321A
TtME I OIV
SX MAG
OFf
SX MAG
ON lpultl
Unmag nified WoYefarm
rr . .. . I l ., ... ·.·
!:-_ • b. .::t- r:: f=
jY I ''T ~ ·t.-rl 1-;--
rr" ·
1
~ ..
t- i- " lr ..... t::- L_L_
/ \
I \
/ I \
/ ' \
r- rl ... ..... .. .. - r- l- r-
1' - .. ... ··· ~ ·1-
t:: .. -++ ++~~ ~
.... . -l ..l ~-
r- - ~· =Fi::t -H~ :Ft-~
~ ~ .... - ...... ·-'-J.......L...J
Magnified WaYefMm
Fig. 3·
3. Operotlon of the s weep magnifier .
Sweep Triggeri ng
T he oscilloscope display is formed by the repetitive sweep
of the spot across the oscilloscope screen. If the sweeps ore
allowed to occur at random, or a rote unrelated to the input
waveform, t
he di sp layed waveform will be !raced out at a
different point on the screen with each sweep. This will
either ca use the waveform to drift across the screen or to be
indistinguisha
ble .
In most ca s es it is desirable for repetitive waveforms to
appear st ationary on the oscilloscope screen so that the
characteristi
cs of the waveform can be examined in delail.
As a necessa ry condition for this type of display, the st art
of the sweep must bear a definite, fixed-time relationship to
the observed waveform.
This means that each sweep must
start at the some time, relative to some point on lhe observed
waveform.
In t he Type 321 A, this is accomplished by start-
ing or triggering the sweep with the displayed waveform, or
with another waveform bearing o definite time relationship
to
the displayed waveform.
The wav ef orm used to start the horizonlal sweep is called
a "triggering signa
l'' (whether it is lhe waveform being ob-
served, or some other wa vefo rm) . The following instructio ns
tell you how to select the triggering signal source.
Selecting the Triggering Source
In preparing the Type 321 A Oscilloscope for triggered
operation
of t he sweep, it is first necessary to se lect lhe
triggeri ng signal source which will provide the best display
fo r the particu lar application. The sweep con be triggered
by the displayed waveform,
or by on externally derived
waveform.
This selection is mode by the setting of the IN T.
EXT switch (see Fig. 3-4). Each type of tr ig ger ing has certain
advantages for
some app lications.
Triggering fr
om the displayed waveform is the melhod
mosl common ly used. T he displayed waveform is selected
when the tNT-
EXT switch is in the INT position. Internal trig-
3-3

Operating In structions - Typ e 321 A
gering is convenient since no external triggering connections
ore required. Satisfactory results ore obtained in most appli-
ca tions.
To trigger the sweep from some elCternal waveform, con-
nect the triggering waveform to the !TRIGGERING)
INPUT
connedor and place the !NT-EXT switch in the EXT position.
!External triggering provides definite advantages over in-
ternal tri gger iog in certain cases.) With external triggering,
the triggering signal usually remains constant in amplitude
and shape. It is thereby possible to observe the shaping and
amplification of o signal in on external circuit without reset-
ting the oscilloscope triggering controls for
each observation.
Also, time
and phose relationships betvtccn the waveforms at
different points in the circuit can be seen. If, for example ,
the external triggering signal is derived from the waveform
at the input to o circuit, the time relationship and phose of
the wa veforms at each point in the circuit ore compared to
the input signal by the display presented
on the oscilloscope
screen.
Selecting the Triggering Slope
T he horizontal sweep con be t riggered on either the rising
or falling portion of the triggering waveform. When the
SLOPE switch is in the + position, the sweep is triggered
on the rising portion of the triggenng waveform; when the
Displayed Wa veform
-
'--- "----
tNT
SLOPE switch is in the -position, the sweep is tri ggered on
the fatting portion of the waveform (see Fig. 3-5).
In many applications the triggering slope is not im portant
since triggering
on either slope witt provide o display .suitable
to the application.
Selecting the Triggering Mode
Aut omatic Mode
Automatic triggering is obtained by rotating the (TRIG-
GERING! LEVEL control fully counterclockwise to the AUTO
position.
This mode allows triggering ot t he average voltage point
of the applied waveform. Also, the sweep runs at approxi -
mately a 50-cycle rote when no triggering signals ore Op·
plied; this produc es a reference tr ace or baseline on the
screen. Automatic triggering con be used with both internal
and external triggering signals, but for most waveforms
tt is useful only for triggering at frequencies above 50 cycles.
Automatic triggering saves considerable time
in observing
a series
of waveforms since it is not necessary to reset t he
triggering level for each observation. For this reason it is
the mode that is normally used. Other modes ore gen erally
used only f or spec i al app lic ations, or where stable trigger-
in g is not attai nab le in the automatic mode.
Extem al Trigger ing Waveform
E X T------------~
I NT-EXT
Switch
INP UT
Os<llloscope
Sw.ep·Starting
C ircyih
Fig. 3-4 The triggering sillr>af Is selected from two pon i ble soYrcet with the INT-EXT switch.
3-4

SL OPE
Swee p T tlggers
On - Slope
SLOPE
Sweep Tt lggeu
On ,_ Slope
Op era ting In stru ct ions -Type 321A
L\ (
~ L \
1
~
\
j_
l 1
ll 1 J v
J
i
l I
~.I
Wa vefot ml obtained with t he tr ig-
gering level control se t In the
- r egion.
~
! l\
~
.1ll
~
1\
\
J '
.I
v 1 1 /
~
r l\
\
'
~
\ I
\ j
~ L 1\ v
I _\ v
1\
If '
,J
~ 1
L .. ~ lL
Wav eforms obtain ed with t he trig-
ger i ng le vol con trol set In the
+ region.
( \
r'
IJ
\ l
I ~
' 1 \
~ .. /'
\
.\
\
J
~)
r
I.
~
~
F ig. 3-5 . Effects on the osdlloscope display produced by + ond - uHings of the SlOPE and LEVEL controls .
3-5

Operating Instructions - Type 321 A
Ac Mode
Ac-mode triggering is obtained by setting the AC-DC
switch to the AC position. This mode provides stable trig-
gering on virtually all types of waveforms. As o general
rule, however, the oc mode is unsatisfactory for triggering
with low amplitude waveforms at frequencies below approxi-
mately 15 cycles. This fi gure will vary depending upon the
amplitude and shape of the triggering waveform and should
not therefore be set as on absolute standard . Tr igge ring a~
frequenc.it?s below 15 cycles con be accomplished when
hi gher amplitude triggering signals ore used .
In the oc mode, the triggering point depends on the
overage voltage level of the triggering signals. If the tr ig-
gering signals occur or random, the average voltage level
will vary causing
the triggering point to vary also . This shift
of t he triggering point moy be enough so that it is im poss ib le
to maintain o stable display. In such cases you should use
the de mode,
De
Mode
De mode triggering is obtained by selling the AC.DC
switch to the DC position. This mode of triggering is par -
ticularly useful in triggering from waveforms which ore no~
adop t able to the oc mode , such os random pulse trains or
very low-fre quency waveforms. Random pulse trains pose
o special problem in the oc mode since the random occur-
rence of the input waveforms causes t he overage voltage
level to shift. This in turn may cou~e the triggering level to
shift to on unstable po int. This prob l em is no t encountered!
in the de mode since the triggering point is determined only
by instantaneous voltages.
In the de mode, when the triggering signal is obtained
from the Vertical Amplifier, varying the VERTICAL POSITION
control will change the tri gger ing point. For th is reason ,
you may find it necessary
to readjust the LEVEL control when 1
you change the vertical position of the trace. To eliminate
this effect,
you con use the oc mode provided the triggering
signal
is otherwise suitable for this mode of operation . In
the de mode, t he de level of the e xt ernal triggering signals:
will also effect the triggering point . Generally, when the
triggeri ng signal is small compared to its de level, the oc
mode should be used.
How to Set th e Tr iggering Level
In the oc and de triggeri ng modes, the LEVEL control
determines the voltage le'lel on the triggering wo•teform at
which the sweep is triggered. Using this control, the sweep
c on be continuously triggered at any point on t he waveform
so lo ng as the slope of the waveform is great enough to
provide stable triggering. In the de mode, the ~weep cannot
be triggered with any degree of stability ot the top of o
square wove , for example, because t he time that the voltage-
remains constant is comparatively long. As a result, the
sweep triggers ot random points along the top of t he square
wove, produc i ng considerable trace jitter.
You can use the some metnod to set the LEVEL control for
eith
er t he oc or de. mode. After selecting the triggering1
slope, rotate the LEVEL control fully counterclockwi se to the
AU TO position. Then rotate the LEVEL control clockwi se
until the sweep no l onger triggers. Continue to rotate the
control in the clockwise direction until the sweep again trig-
gers and o stable display is obtained. Further rotation of the
control in the clockwise direction causes the sweep to trigger
ot more positive points on the triggering waveform. ln the
fully clockwi se direction the trace will free run (Fig. 3-51 .
FREE-RUNNING OPERATION
With the Type 321 A, you con get o periodic, free-running
sweep, inde pendent of any externa l triggeri ng or synchroniz-
i ng signal, by rotating the LEVEL control fully clockwise to
the FR
EE RUN position. This permits you to observe t he trace
without on input signal. This trace con then be used to pos i·
lion the sweep or to e~toblish o voltage reference line. The
difference
between the traces produced in the AUTO position
and the FREE RUN pos i ti on is the repetition rote. The repet i-
tion rate in the FREE RUN position is dependent upon the
setti ng of the timing switch. The repetition ro le in the AUTO
position is fixed ot approximately 50 cycles. At the fester
sweep roles, the trace in the AUTO pos ition will appear to
be dim. In the FREE RUN position the trace intensity remains
essentially constant for all
sweep rates.
VERTICAL DEFLECTION SYSTEM
Input Coupling
Input signals to the Vertical Amplifier con be eit he r ac - or
de -coupled by placing the AC·DC.GND switch in the ap -
propriate AC or DC position. De coupling appl i es both the
oc and de components of the input signal to the vertical
amp lifier circuit. This permits measurement of the de voltage
level os well os the amplitude of the oc com pon ent . It is
sometimes neither necessary nor desirable to display the de
component, ho wever, ond in such cases as coupling should
be used. Th is is accomplished by setting the AC-DC-GND
switch to AC. With oc coupling, a capacitor is placed in
series with the input connector to block the de component
while allowing
the oc component to be displayed.
Placing t
he AC-DC-GND switch to the GND position
grounds
the input circuit of the vertical amplifier to provide
o de zero reference. In this position the switch internally dis.
connects,
but does not ground, the applied sign al to the
input connector. Thus, the
GND position eliminates the usual
need for externally ground i ng the (Vertical Amplifi er} INPUT
connec1or of the T ype 321 A or the probe tip to establish o
ground reference.
Deflection Factor
The electrical waveform to be observed is applied to the
(Vertical Amplifier) INPUT connector. The waveform is then
appl i ed through the vertical- def lecti on system to cause the
spot to be def l ec t ed vertically lo trace out the waveform on
the screen of the crt. The VOLTS/DIV switch controls the
vertical def lection foetor in acc u rate ly calibrated steps. T he
VARIABLE control provides uncalibroted variable deflection
fac1ors between the fixed steps of the VOLTS/DIV sw itch.
The
VAR IABL E control has 360° rotati on range and o detent
positi on when t he control is set to CALIB .

NOTE
To make the defle c tion foetor equal to that indi -
cated by the VOL TS / DIV switch, set the VARIABLE
c ontrol to the CALIS detent position.
De Balance Adju stment
The need for adjustment of the DC BAL control is indi-
cated by a vertical shift in t he position of the trace as the
VARIABLE (VOl TS /DIV) control is rotated. This adjustment
should be made as follows:
1. Set the AC-DC-GND switch to GND .
2. Set the oscilloscope controls for a free-running trace.
3. Rotate the VARIABLE (V OLTS /DI V) control bock and forth,
and adjust the DC BA L control simultaneously until the
trace position is no longer affected by rotation of the
VARIAB LE control.
Input Signal Connections
Certain precautions must be observed when you are con·
necting the oscilloscope to on input signal source. This is
to insure that accurate information is ob tained from the
oscilloscope display. This is particularly true when you
are observing low· level signals, or waveforms containing
high· or extremely low-frequency componen ts . For applica-
tions where you ore observing low -level signals, shielded
cables should be used whenever possible,
with the shield
connected to the
chassis of both the oscilloscope and th re
signal source. Unshielded input leads ore 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 signals ore oc-coupled to the
oscilloscope.
2. High-frequency waveforms ore not properly terminated.
3. The input waveform contains high-frequency components
which exceed
th e bandpass of the oscilloscope.
You
must be aware of the limitations of the ins trumen l.
In analyzing t he displayed waveform, you must consider
the
lo ading effect of the oscilloscope on the input signal
source. In most cases this loading effect is negli gib le; how -
ever, in some applications loading caused by the oscilloscope
may materi ally alter the results obtained. In such c ases you
may wish to reduce the amount of load ing to a negligi ble
amount through t he use of o probe.
Use of Probes
Occasionally connecting the input of an oscilloscope to
a s ig nal source lo ods the source sufficiently to adversely
affect bo th the operation of the source and the waveform
displayed on the oscilloscope. In such cases an altenuotor
Op erating Instructions - Type 321A
probe may be used to decrease both the c apa citive a nd res is-
tive load ing caused by the oscilloscope to a negligible value.
In add itio n to providing isolation of the oscilloscope from
the signal source, on ottenuator probe also decreases t
he
amplitude of the displayed waveform by the attenuation
foe t or of the probe. Use of the probe allows you to increase
the vertical-deflection fa ctors of the oscilloscope to observe
la rge·amplitude signals beyond the normal limit s of the
oscilloscope. Signal amplitudes, however, must
be limited to
the maximum a llow able value of the probe used. When
making amplitude measurements with on attenuator probe,
be sure to
mu lti ply the observed amplitude by the attenua-
tion of the probe.
If the wav eform being displayed has rapidly rising or
falli ng voltages, it is generally necessary to clip the probe
ground lead
to the chassis of the equipment being tested.
Select a ground point near the po int of measurement, as
shown in Fig. 3-6.
Fig. 3-6 . C onnecting a pr obe to the Input signal source.
Before using a probe you must check (and ad just if neces-
sary) the compensation of the probe to prevent distortion of
the appl ied wavefo rm. The probe is compensated by adjust-
ing the control located in the body of t he probe. Adjustment
of the pr obe compensates for variations in in put copocitonce
from one ins trum en t to another. To insure the accuracy of
pulse and transient measurements, this adjustment should be
checked frequently.
To
adj us t the probe compensation, set the VOLTS/DIY con·
trol to the .01 position and the LEVEL control to the AUTO
position. Set the SLOPE switch to + and the lNT-EXT sw itch
to INT. Connect
th e probe tip to the CAL OUT 500 MV con·
nectar. Set the TIME/DIV switch to .5 M IL LI SEC ond adjust
the probe to obtain flat tops on the displayed squ ar e wove·
form ( see Fig. 3-7 .)
3-7

Operating lnstn.~ction s - Type 321A
Voltag e Measurement s
The Type 321 A Oscilloscope can be used to measure the
voltage of the input waveform by using the calibrated ver-
tical-deflection factors of the oscilloscope. The method
used for all voltage measurements is basically the some
although the actual techniques vary somewhat depending on
the types of voltage measurements, i.e., ac-component volt-
age measurement s, or instantaneous voltage measurements
wi
th respect to some reference potential. Mony waveforms
contain both ac and de voltage components, and it is often
necessary to measure one
or both of these components.
When making voltage measurements, you should display
the waveform over as large a vertical portion of the scree111
os possible for ma)(imum accuracy. Also, it is important that
you do not include the width of the trace in your measure-
ments . You should consistently make all measurements from
one side
of the trace. If the bottom side of the trace is used
for one reading, it shou ld be used for all succeeding read-
ings.
The VARIABLE (VOLTS/DIVl control must be in the
CALIB detent position.
Ac Compon en t Voltage Measurements
To measure the oc component of a waveform, the AC-DC-
GND sw itch shou ld be set to the AC position. In this position
only the oc components of the input waveform are displayed
on rhe os cilloscope ~ <: rcen . However, when the ac compon en i
of the input waveform is very low in frequency, i• will be
necessary lor you to make voltage meosuremenh with the
AC DC-GND switch in the DC position.
To mo~e o peok· la ·pcak voltage measurement on the oc
component of a waveform, perform the following steps (see
Ftg.
3-81 .
lncorre <t
Adfu•ted Corr ed ly
1. Wi th the aid of the groticule, measure the vertical dis-
tance in divisions from the positive peck to the negative
peak.
2. Multiply the setting of the VOLTS/D IY control by the dis-
tance measured to obtain the indicated voltage.
3. Multiply the indicated voltage by the attenuation foetor
of the probe you are us i ng to ontain the true peale-to-peak
voltage.
As on example of this method, assume that using the
P6006 Probe and a deflection foetor of 1 volt per division,
you measure o vertical distance between peaks of 4 divisions.
In this case, then, 4 divisions multiplied by 1 volt per divi-
sion gi ves you on indi ca ted voltage of 4 volts peale-to-peak.
The indicated voltage multiplied by the probe"s attenuation
factor of 10 then gives you the true peak-to-peak amplitude
of 40 volts.
When sinusotdal waveforms ore measured, the peak-to-
peak voltage obtained con be converted to peak, rms, or
overage voltage through
use of standard conversion fae1ors.
Instantaneou s Voltag e Measurements
The method used to measure instantaneous voltages is
virtually identical to the method described previously for
the measurement
of t he ac componenl$ of a Vtoveform. How-
e.,.er, for instantaneous voltage measurements the AC-DC-
GND sw i tch must be placed in the DC position. Also, si nce
instantaneous voltages ore measured with respect to some
potent ial (usually ground), a reference line must be
es t abl i shed on the oscilloscope screen which corresponds to
that potential. If, for example, voltage measurements ore to
be mode with respect to +
100 volts, lhe reference line would
correspond to +1 00 volts. In the follow ing procedure a
method is presented for es!ablisning this reference li ne at
ground, since measurements with respect to ground ore the
P6006 Pr obe--Mo ld probe ba rrel ond
l oo sen locki ng sl ee ve st v erot turns. Hold
probe bo se while odufstlng pr ob• ba rrel
for flat -top squar e wav es. Hold pro b•
barrel and carefully ti gh te n locki ng
al .. vt .
F/9.
3- 7. T h ~ pr ob e is od fusted to ob ta in o, und l< torod pt ese ,t all on of the c,aHbr olo r s quar ewa v o.
3-8

Operating Instruction $- Type 321A
Fi g. 3·8. Mea suri ng the peak - to-p e ak at voltage of on ap p lied waveform .
most common type. The some general method may be used
to measure voltage with respect to any other potential, how-
ever,
so long os that potenti al is used to establish the re f.
erence line.
To
obtain on int antoneous voltage measurement with res·
pect to ground, or some other voltage, perform the following
steps (see Fig. 3-
9) .
1. To establ is h a ground reference line, se t the A C - DC ~
GND switch to GND . Or , to establish a reference line
which represents a
voltage other than ground, touch the
probe tip to the voltage and leove the AC-DC-GND
switch ot DC. Then adjust the osc ill oscope controls to
obtain o free-running sweep . Vertically pos iti on the trace
to a convenient point on the oscilloscope screen. This
point will
depend on the polarity and amp litude of the in -
put signal, but should a lwa ys be chosen so that the trace
lies along one of the ma jor divisions of the groticule.
The graticule division corresponding to
the position of
t he trace is the voltage reference line and all voltage
measurements must be mode with respect to th is line.
(Do not odjust
the VERTICAL POSITION control ofter the
reference line has been established .)
2. If ground reference was established, set the AC.DC- GND
switch to DC ; if a reference line ot her than ground was
established, remove the probe tip fr om this voltage and
connect it to the signal source. Adjust the LEVEL control
for o s
ta ble display.
Probe Att e nuor i on Fac tor
VOLTS / OIV Switch Se lling Verti ca l Oefled l on
From Reference ll no
Ins tantaneou s
Vol tage With
= Re1pe ct To
Reference Voltage
Fig. 3-9 . Meo s ur i ng the ln• ta n la ne ou s vo ltag e wit h r espe ct to gr ound l or some oth or rof erenco vo lt age I.
3-9

Op & ra tl ng Instructi on s- Type 321A
3. Measure the vertical distance in divisions from the desired
point on the waveform to the voltage reference line.
4. Multiply the sett i ng of the VOLTS/DIV control by the dis·
tonce measu red to obtain the indicated voltage.
S. Mu lhply the indicated voltage by t he attenuation foetor
of the probe you ore us ing to obtain the actual voltage
with respect to ground (o r other re f erence voltage).
As on example of this method, assume you ore using the
P600 6 Probe and a deflection foetor of 0.2 volt per division.
Alter setting the voltage reference line ot the
second from
bottom
divi sion of the grati cul e, you meo~ ure o distance of
3 divisions to the point you wish to check . In this case,
3 divisi ons multiplied by 0.2 volt per division gi ves you on
indicated 0.6 volt. Since the voltage point is above the
vo ltage reference li ne the polarity is indicated to be pos i-
tive. The indico•ed voltage multiplied by the probe attenua-
tion foetor of 10 then gives you the actual voltage of +6
volts.
App r opriate TIME / DIV Switch SeHi ng
Time Measurements
Tho ca librated sweep of the Type 321A Oscilloscope causes
any hor izontal distance on the screen to represent o definite
known interval
of time. Using this feature you con accurately
measure
the time lapse between two events displayed on
the oscilloscope screen. One method which produces suf -
ficient accuracy for most opplicotions is as follows (see
Fig . 3-10) .
1. Meosure th e horizontal distance between the two di s-
played events whose time interval you wish to find.
2. Multiply the distance measured by the seHing of the
TIME /DIY control to obtain the apparent time interval.
(The VA RIABLE TIME/DIY control must in the CALIS posi·
tion.l
NOTE
D ivide the apparent time interval by 5 if the mag·
nifier is on.
Horl~ontal Distance
n me
Fig. 3· 10.
Measur ing the interv a l betwee n even I$ d is play ed on the oultlo,cope " run .
3- 10