Tektronix 321 A User manual

INSTRUCTION
IVIA.NUA.L
Tektronix,
Inc.
Serial
Number
____
_
TYPE
321A
OSCILLOSCOPE
;1~
8
'7
/I
'19'1
S.W. Millikan
Way
•
P.
0.
Box
509
•
Beaverton,
Oregon
97005
•
Phone
644-0161 •
Cables:
Tektronix
070-0425-01
169

Type 321A (SN 100-5999)
questions with ·respect to the
mention,d above should be taken up
Tektr()nix Field Engineer.
repair and replacement-part
,,~ser'vil~e is geared directly to the .field, there-
, .. ,,.- .. ,... all r~quests for reF>ca.irs and replc;ace~
parts ~hould be directed to the Tek-
l>•'t~onix Field Office or:· ~epresentative in your
This pr9cedure will assllre you the
.· t·a.S1iest possible service. Please inc:ludet~~.
Type and Serial number with aH
••t~~~':t:e(;i6E~sts for parts or service.
and price .change priv.:
© 1964, ~eyt materiq;l .copy-
by Tektronix[ Inc., Beaverton,
Printed in the .United States of
rica. AW r~~hts re$erved. Hontents
his publicqti~o ma~, flOt. be reproduced
ny form without pe.-m~ssion .of the copy-
t
owner.
®

®
Type
321A
(SN
100-5999)

I I
The
Type
321
A
Oscilloscope.
Type
321A
(SN
100-5999)
®

Type
321A
(SN
100-5999)
SECTION J
·cHARACTERISTICS
Introduction
The Tektronix Type
321
A
is
a high-performance, dc-to-6
me, transistorized oscilloscope.
Its
light weight, small size
and
ability to
operate
from a variety
of
power
sources make
it
a versatile field
and
laboratory
instrument. The oscillo-
scope
can
operate
from its internally-contained
rechargeable
battery
pack,
an
external
de
source
or
from a 115/230-volt
50-800 cycle
ac
line. Regulated
power
supplies
in
the instru-
ment,
accurate
calibration,
and
precise linearity
assure
exact
time
and
amplitude
measurements
despite
normal
voltage-
source
and
power-supply-load
changes
that
occur under
actual
operating
conditions.
Operating
temperature
range
derived
from tests indicates
optimum
performance
and
reliability on
its
self-contained
batteries
from 0
o
to
+40
o
C
at
altitudes up to 15,000 feet.
Temperature
range
without
batteries
when
operating
from
an
external
source
is
-15
o
C to
+55
o
C.
Non-operating
tem-
perature
range
is
-55°
C to
+75°
C without batteries
and
-40°
C
to
+60°
C with
batteries
at
altitudes to
50,000 feet.
For the
operator's
convenience, a front-panel
battery
light
indicates when
the
internal batteries
are
low. If
external
de
or
ac
operation
is
being
used
instead
of
the
batteries,
the
light turns on
if
the
external
voltage
source
drops
too
low
for
proper
power
supply regulation.
A 4-position
power
switch on the front
panel
permits
convenient selection
of
charging
rate
and/or
power
source.
Vertical Deflection
System
Bandpass-De
to
at
least 6
me
(3-db down) using
de
cou-
pling; using
ac
coupling, low-frequency
3-db
down
point
is
2 cps typical from a 1-kc reference.
Sensitivity-0.01
v/div
to
20
v/div
in
11
calibrated
steps;
accuracy
is
within
3%
of
front-panel markings. Con-
tinuously
variable
from
0.01
v/ div to
about
50
vI
div
uncalibrated.
Input
lmpedance-35
pf nominal
paralleled
by 1 megohm
(+
1%), 8.2 pf nominal
paralleled
by
10 megohms
(+2%)
when using
the
P6006
lOX
Probe.
Maximum Allowable Input
Voltage
Rating-600
volts com-
bined
de
and
peak
ac; 600 volts (not 1200 volts) peak-to-
peak
ac.
Triggering
®
Type-Automatic,
or
amplitude-level selection using pre-
set
stability.
Mode-Ac-coupled
or
De-coupled.
Slope-Plus,
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 major division vertical
deflection
at
1
kc
increasing
to
1 major division
at
6 me.
External: 1 volt
peak-to-peak
at
1
kc
increasing
to
3 volts
peak-to-peak
at
6
me.
Nominal input
impedance:
5 pf
paralleled
by 100 kilohms
(+20%).
Sweep
Type-Miller
Integrator.
Sweep
Rates-0.5
J.LSec/div
to 0.5
sec/div
in
19
calibrated
steps.
Accurate
5X
sweep
magnifier
extends
calibrated
range
to
0.1
JLSec/
div.
Calibrated
sweep-rate
accuracy
is
+3%.
Sweep
time
adjustable
between
steps
and
to
2:1.5
sec/div
uncalibrated.
External Horizontal Input
Bandpass-De
to
at
least 1
me
(3-db down).
Deflection
Factor-1
v
/dv
+
10%
with
5X
magnifier on.
Input
lmpedance-30
pf
typical
paralleled
by
100 kilohms
{+5%).
Amplitude Calibrator
Square
Wave-Frequency
about
2
kc.
Amplitude-500
mv peak-to-peak. Also
40
mv peak-to-
peak
internally
coupled
in
CAL
4
DIY
position
of
VOLTS/
DIY
switch. Peak-to-peak
amplitude
accuracy
is
+3%.
Cathode-Ray Tube
Type-Special
Tektronix-manufactured T3211. 3
11
flat-face,
post-deflection
accelerator.
Low
heater
power.
Accelerating
Potential-4
kv.
Z-Axis
Modulation-External
terminal permits
RC
coupling
to
crt grid.
Unblanking-Deflection
unblanking.
Phosphor-Type
P31
normally furnished;
Pl,
P2, P7,
and
Pll
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
1
0-horizontal
1
/4
11
divisions.
Power Requirements
Source-Operates
from 10 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

Characteristics-Type
3~1A
(SN
100-5999)
ampere-hour
cells),
or
11.5 to 35 volts de (aircraft, auto,
boat,
etc.),
or
103.5 to 126.5 volts
or
207 to 253 volts,
rms, 50
to
800 cycles, single-phase ac.
Power
Consumption-Approximately
700 ma from internal
batteries
or
external de source; 20 watts nominal
at
115-volt
ac
line.
Temperature
Protection-
Thermal cutout switch interrupts
power
if
ambient
temperature
exceeds
131
o F
(55
o
C).
Built-in
battery
charger
is
standard
equipment.
Environmental Capabilities
Vibration
(operating)-0.025
11
peak-to-peak, 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
55 cps on
each
axis.
Shock
(operating)-20
G's, % sine, 11-msec duration.
1-2
Two shocks
each
direction
along
each
of
the
three
major axis: bottom, top, left side, right side, front
and
rear. Total of 12 shocks.
Shock
(non-operating)-60
G's,
1
/2
sine, 11-msec dura-
tion.
One
shock
each
direction
along
each
of the three
major axis; total of 6 shocks.
Humidity
(non-operating)-Meets
Mii-Std-2028, method
106A (except freezing
and
vibration) through 5 cycles
(120 hours).
Transit
(non-operating)-Meets
National
Safe Transit test
when factory
packaged.
Vibration for
one
hour
at
slightly
greater
than
one
G. Eighteen-inch drop
in
any
orientation.
Mechanical Specifications
Construction-Aluminum
alloy chassis
and
cabinet.
Finish-Anodized
panel, blue vinyl-finish cabinet.
Dimensions-8%
11
high,
5%
11
wide,
16
11
deep
overall.
ACCESSORIES
Information
on
accessories for use with this instrument
is
included
at
the
rear
of the mechanical parts list.
®

SECTION
2
Type
321A
(SN
100-5999)
PRELIMINARY
INSTRUCTIONS
Power Requirements
The regulated
power
supplies in the Type
321
A
will
operate
form 115-v
or
230-v
rms
ac line, from an external de source
(11.5 to 35 volts),
or
from a
"battery
pack"
consisting
of
either 10 size D flashlight cells
or
10
size D rechargeable
cells.
Fuse
Data
Use
only
the recommended
fuses
in the Type
321
A Oscil-
loscope. The
upper
fuse,
F621
(see
Fig. 2-1),
is
a 1.5-amp
3AG
Fast-Bioi the
lower
fuse,
F601,
is
a .25-amp
3AG
Fast-
Bio.
Neither
fuse needs to be changed
if
the oscilloscope
is
converted from one line
voltage
to the ot,her (115 v and
230
v).
Fig.
2-1.
Location
of
fuses
and
Charger
switch
(left-side
view) .
Ac Operation
Unless
tagged
otherwise, your instrument
is
connected
at
the
factory
for
operation
at
1
03.5 to 126.5 volts, 50 to 800
cycles ac
(115
volts nominal). However, provisions are made
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 are
normally
connected
in
parallel
for
115-volt operation, but which can
be connected
in
series
for
230-volt operation.
The
primary
windings are marked
1,
2, 3, and
4.
Terminals
1 and 3 are connected to one
winding
and terminals 2 and 4
are
connected to the second winding. The ac input leads are
connected to terminals 1 and 4
for
both 115-volt
ana
230-
®
volt
operation,
so
these connections
do
not
have to be
changed when converting from one line
voltage
to the other.
When
wired
for
115-volt
operation,
terminals 1 and 2 are
joined
by
a bare bus wire, and terminals 3
and
4
are
simi-
larly
joined,
as
shown
in
Fig. 2-2(a).
To
convert to 230-
volt
operation,
remove the bare
bus
wires between these
terminals and substitute a single connecting
wire
between
terminals 2
and
3,
as
shown
in
Fig. 2-2(b).
To turn on the Type
321
A 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.
To
115-v AC
(a)
To
230-v
AC
Fig.
2-2.
(a)
Transformer
connection
for
operation
from
103.5-
126.5
volt
ac
fine;
(b)
connections
for
operation
from
207-253
volt
ac
line.
As long
as
the ac
power
cord
is
connected
to
the ac line,
power
is
being
applied
to the
power
transformer T601, ac-
rectifier circuit, and graticule lights
for
all
positions
of
the
POWER switch.
Application
of
power
to these circuit
is
re-
quired to
provide
battery-charger operation
for
the internal
batteriesi the graticule lights
provide
visual
indication
that
th~se
circuits are
"on".
Power to the
battery
charger itself
is
controlled by a Charger switch
(see
Fig.
2-1
).
If the switch
2-1

Preliminary
Instructions-Type
321A
(SN
100-5999)
is
set
to
LOW
or
HIGH,
the
ac
rectifier
is
connected
to
the
battery
charger
circuit which,
in
turn,
provides
chargif.lg
q.Jr-
rent
to
the
internal
rechargeable
batteries. " -
NOTE
If
dry
cells
are
used
instead
of
rechargeable
bat-
teries,
then
the
Charger
switch
must
be
·set
to
DRY
CELLS
to
disconnect
the
charger
circuit. For
further
information
about
battery
operation,
refer
to
the
topics
titled
"Battery
Operation"
and
"Battery
Charger"
appearing
in
this
section
of
the
manual.
If
the
Type
321
A
is
being
operated
exclusively from
the
ac
line
and
the
internal
batteries
are
removed,
the
Charger
switch
can
remain
in
the
DRY
CELLS
position to disconnect
the
charger
circuit.
If
you
prefer
to
completely
turn off
all
power
to
the
Type
321
A,
set
the
POWER switch to
TRICKLE
and
either
disconnect
the
power
cord
from
the
ac
line
or
turn off
the
power
at
a wall switch (or equiv-
alent).
Battery Operation
Operation
from
the
internal
battery
source
can
be
accom-
plished
by
using:
Loosen
thumb
screw
to
unlock
cover,
then
pull cover
forward
to
-remove.
1.
Ten size D flashlight cells
(approxtmately
1
/2
-hour con-
tinuous
operation,
more
with intermittent
operation),
or
2.
Ten size D Alkaline cells such
as
Eveready
E95, Burgess
AL-2,
or
Mallory
MN-1300
(about
2%
hours continuous
operation),
or
3. Ten size D nickel-cadmium
rechargeable
cells (up to
about
5 hours continuous
operation,
depending
on
the
type
used).
The nickel-cadmium cells
are
the
most
practical
type
where
considerable
battery
operation
is
planned.
To install
the
cells, first
open
the
battery
cover
as
illus-
trated
in
Fig. 2-3.
Next,
install
the
batteries
by
following
the
procedure
given
in
Fig. 2-4.
CAUTION
Be
sure
to
observe
cell
polarity
indicated
on
the
battery
cover.
To turn on
the
Type 321A
when
operating
from
the
internal
batteries,
set
the
POWER switch
to
BATT
ON.
To turn off
the
oscilloscope,
set
the
POWER switch to
one
of
the
OFF posi-
tions-PULL
or
TRICKLE.
These OFF positions disconnect
the
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
the
battery
cover from
the
Type
321
A Oscilloscope.
2-2
®
i
I I

Preliminary
Instructions--Type
321A
(SN
100-5999)
Internal
Battery Terminals
Install .
five cefls
in.
each
side
of
the
battery
holder.
Be
sure
to observe cell
polarity
as
in-
dicated
on
the
cover.
Fig.
2-4.
Procedure for installing
the
batteries.
Battery
Charger
As
mentioned previously, the battery charger
is
connected
to
the internal batteries
as
long
as
the ac
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 can be
obtained
by
using various line voltages
in
combination
with
various settings
of
the POWER and Charger switches. The
table
shows the Type
321
A
wired
for
115-volt nominal line
operation. If the oscilloscope
is
wired
for
230-volt nominal
line operation, the charging currents
will
still be the same
but the ac line voltages
will
be twice the amount shown
in
the table.
Use
Table
2-1
as
an
aid
in
determining the
proper
posi-
tion
for
the POWER and Charger switches
for
the
particular
brand
or
type
of
rechargeable batteries being used in the
Type
321
A.
After
setting the switches
to
their proper posi-
tion, the line
voltage
can then be set to the charging rate
recommended
by
the manufacturer
of
the cells.
An
auto-
transformer having a rating
of
at least 1 ampere and
equipped with an rms-reading ac voltmeter can be used to
set the line voltage.
When
using rechargeable batteries, sixteen hours
of
charging
at
the full rated charging current recommended
by
the manufacturers should be adequate to
fully
charge
the batteries.
Excess
charging may damage the batteries.
®
One
method
for
determining charge conditions
of
the bat-
teries
is
to set the POWER switch to
BATT
ON
and then
measure the voltage across the
battery
terminals
(see
Fig.
2-4). A reading higher than
13
volts indicates that· the
batteries are
fully
charged. A reading lower than
13
volts
indicates that more charging time
is
required.
As
mentioned previously,
if
dry
cells are installed
in
the
battery
holder and the Type
321
A
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
POWER*
Charger
Aproximate
Charging
Switch
Switch
Current
in
Ma
Position
Position
103.5
vl109
vl115
v 121 v
126.5
v
1==:
EXT
ON
LOW
I
20
I
24
1
27
31
33
HIGH
I
22
I
26
[30
33
35
TRICKLE
I
LOW
I
31
I
34
I
38
41
44
HIGH.
34
I
37
I
41
44
48
FULL
I
LOW
I
160
I
180
I
200 220 230
HIGH
290
I
320
I
360 380 410
*The
BATT
ON
position
is
not
included
in
the
table
because
the
Type
321
A
should
not
be
operated
from
the
ac
line
and
the
batteries
at
the
same
time,
Reason:
Battery
drain
exceeds
charg-
ing
rate.
2-3

Preliminary Instructions-Type 321A (SN 100-5999)
De Operation
Operation from an external de source is acomplished by
connecting the special pigtail-type de power cord in the
proper manner.
For 11.5- to 20-volt operation, the black
(+) and white (-) leads are connected to the voltage
source;
for 20- to 35-volt operation, the green ( +) and white
(-) leads are connected to the voltage source. When the
connections to the external de voltage source are properly
made, the external
de source is floating with respect to the
Type 321A chassis. Up to 600 volts difference is permissi-
ble, if necessary.
To turn on the Type 321A, set the POWER switch to EXT
ON. To turn off the oscilloscope, set the POWER switch to
one of the
OFF positions-TRICKLE or FULL.
When operating from the external de 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 same time.
NOTE
The internal battery charger circuit is disconnected
during external de operation. Therefore, external
batteries (if used as the de source)
cannot be
charged by connecting the line cord to the ac line.
Also,
an external de source cannot be used to
charge the internal batteries since the POWER
switch does not electrically connect the two
sources together.
LOW BATTERIES Light
The LOW BATTERIES light turns on when the following
conditions exist:
1. The POWER switch is set to BATT ON and the internal
batteries drop to
11.5 v ( +0.2 v) or lower.
2. The POWER switch is set to EXT ON and the external
source voltage
is low enough to cause the Type 321 A un-
regulated voltage to drop to about 11.5 v or lower.
NICKEL-CADMIUM BATTERY INFORMATION
General
The nickel-cadmium battery cells available for use with
this instrument have been selected as a result of extensive
evaluation.
Each battery cell has received an ampere-hour
test, has
met or exceeded the minimum ampere-hour storage
requirement and has been rigidly inspected.
The battery
cells used in this instrument should provide a useful operating
life extending over several hundred charge-discharge cycles.
Precautions
To extend the useful operating life of the nickel-cadmium
battery cells used in this instrument, observe the following
precautions.
1. Do not exceed the recommended charge rate and per-
iod (see Charge Rate discussion which follows).
2. Be sure the battery charger is operated correctly as
described previously
in this section.
3. Be sure to observe the cell polarity when inserting the
batteries
(see Fig. 2-4).
4. Excessive discharge of the batteries after the LOW BAT·
TERIES light comes on may cause one or more of the cells
to reverse polarity. Although the cells are protected against
immediate damage, repeated polarity reversal
will shorten
the
useful life of the batteries.
Observe the temperature
limits given in the following infor-
mation for charging, operation and storage.
Maintenance
When the battery cells are overcharged or when dis-
charged to the point of polarity reversal, gas is formed
within the nickel-cadmium cells which produces an internal
pressure.
The nickel-cadmium cells supplied by Tektronix,
Inc. (Tektronix Part No. 146-0010-00) incorporate a vent so
this internal pressure does not damage the battery. However,
as the internal pressure
is relieved, a small amount of the
electrolyte may
be expelled with the gas. Although the cell
will probably not be damaged, this loss of electrolyte may
result
in shorter overall battery life. The batteries and bat-
tery compartment should be inspected occasionally
for any
electrolyte residue
on the batteries themselves or in the
battery compartment.
Any residue which is found should be
cleaned away
with a 2% solution of boric acid in water.
A
2% solution of boric acid can be obtained by dissolving
about 1
1f4 teaspoons of boric acid powder in one cup of
water.
After the residue has been cleaned from the batteries
and the battery compartment, dry the wetted area throughly
with a soft cloth.
If the total potential across the battery terminals (see Fig.
2-4) does not reach 13-14 volts even after the recommended
charge
time, one or more of the battery cells is probably
defective.
To locate the defective cell, first be sure the bat-
teries have been charged
for the recommended charge per-
iod.
Then, while operating the instrument on the internal
batteries, measure the potential across each individual
cell.
Use a meter which has a long, thin tip to reach the positive
contact between the batteries. If the individual battery
cell
measures below about 1.2 volts it is probably defective;
above
this voltage tbe battery cell is probably operating "
correctly.
If the total potential across the battery terminals
is 13·14 volts after the recommended charge period, but
the
LOW BATTERIES light comes on too soon when operating
on internal batteries, the charge retaining capacity of one
or
more of the battery ceils has probably decreased below
the acceptable
limits. (NOTE: Batteries may not be reaching
full charge due to a defective charger circuit.) This can be
checked
in a manner similar to that described above. First,
be sure that the batteries have been charged for the recom-
mended charge period. Then, operate the instrument on the
internal batteries
until the LOW BATTERIES light comes on.
Now measure the potential across each cell. If an individual
cell measures below about 1.2 volts, it is probably defective;
above
this voltage it is probably acceptable (NOTE: If the
voltage of all the
cells is above 1.2 volts and the charger
circuit
is operating correctly, the LOW BATTERIES circuit may
be at fault.)
When replacing battery cells in this instrument, charge the
entire set of batteries
at the recommended charge rate and
charge period before operating the
instrument from the inter-

nal
batteries.
This
protects the new
cells
from
polarity rever-
sal damage.
The
batteries should be replaced only
with
the
cells
which have the same charge rate and charge capacity
as those
in
the instrument
(see
Charge
Rate
for more informa-
tion).
Replacement
cells
obtained
from
Tektronix,
Inc.
(Tek-
tronix Part No.
146-001
0-00)
have solder tabs
on
each end.
These
cells can be soldered together
to
reduce inter-cell
contact resistance.
Charge Rate
The
batteries
in
this
instrument can be charged over an
ambient temperature of
oo
C
to
+40°
C.
However, maxi-
mum
operating
time
is
provided when the batteries are
charged
at
about
+25°
C
The
HIGH
position of the
Charger switch can be used.
This
position of the Charger
switch provides about
400
milliamperes
of
charging current.
A charge period of
14
to
16
hours should be sufficient
to
charge the battery
cells
to
their
full
potential. Although the
batteries may not be damaged
by
longer charge periods
at
this
rate, the
useful
life
of the battery
will
be shortened.
If
it
is
desired
to
maintain a
full
charge
on
the batteries,
use
the
TRICKLE
position of the
POWER
switch. A trickle charge
is
also applied to the batteries when operating
from
an
external power source.
Replacement battery
cells
obtained
from
sources other than
Tektronix,
Inc.
should be charged
in
the
LOW
position
of
the
Charger switch
unless
the manufacturer's specifications state
that
it
will
withstand a 400-milliampere charge rate.
It
can-
not be assumed that the replacement battery
cell
will
with-
stand the
HIGH
charge rate even though
it
has
the same
ampere-hour rating as the batteries supplied
by
Tektronix,
Inc.
The
LOW
position of the Charger switch provides a
charge current of about
200
milliamperes.
During normal usage or storage, the individual battery
cells
in
this
instrument attain slightly different charge char-
acteristics.
To
provide the best overall operation and maxi-
mum
operating
life,
the charge
on
the battery
cells
should be
equalized periodically.
This
can be done without damage
to the battery cells by charging the batteries
at
the
full-
charge rate for
24
hours.
This
should be done after every
®
Preliminary
Instructions--Type
321A
(SN
100-5999)
15
charge-discharge cycles or every 30 days, whichever
occurs
first.
Battery Operation
This
instrument can be operated on the ·internal batteries
over an ambient temperature rqnge of
-15°
C
to
+40°
C.
However, the
maximum
operating
time
and
useful
battery
life
is
provided between + 15° C and
+25°
C.
For
example,
batteries
fully
charged
at
+25°
C
to
+30°
C
will
provide
about 5
1
/2
hours of operation but only about 4 hours
of
operation when charged
at
+40°
C.
The
instrument should not be operated
from
the internal
batteries after the
LOW
BATTERIES
light comes on.
This
light
is
an indication that the battery potential has dropped below
the
level
necessary for correct power supply regulation.
Further discharge of the batteries beyond
this
level not only
provides inaccurate measurements but
it
may cause one or
more of the
cells
to
reverse polarity.
Battery Storage
The
battery
cells
used
in
this
instrument may be stored
in
a charged or partially charged condition.
For
best shelf-life
when storing individual cells,
fully
recharge the battery cells
at
three
to
six
month intervals. Although replacement
cells
obtained
from
Tektronix,
Inc.
are
fully
charged before ship-
ment, recharge the complete set of batteries before operating
the instrument.
Charge retention characteristics of nickel-cadmium
cells
vary
with
the storage temperature. They may be stored
at
any temperature between
-40°
C and
+60
o
C without
damage, either
in
the instrument or as individual cells.
How-
ever, the self-discharge rate increases
with
ambient tempera-
ture.
For
example,
cells
stored
at
+20°
C
will
lose about
50% of their stored charge
in
three months but when stored
at
+50°
C,
they
will
be almost completely self-discharged
in
30 days.
High
humidity also increases the rate of self-dis-
charge. If
this
instrument
must
be stored
at
either high ambi-
ent temperature or
high
humidity for an extended period of
time,
it
is
recommended that the batteries be continuously
trickle charged
using
the
TRICKLE
position
of
the
POWER
switch.
2-5

NOTES

SECTION 3
OPERATING
INSTRUCTIONS
General Information
The Type
321
A Oscilloscope
is
an extremely versatile in-
strument,
adaptable
to
a
great
number
of
applications.
How-
ever,
to
make full
use
of
the instrument,
it
is
necessary that
you understand completely the operation
of
each 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 have
very
little
difficulty
in understanding the
operation
of
the
Type
321
A.
The function
of
many controls
is
the same
as
the function
of
corresponding 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 intensity to suit the
ambient
light
conditions and changes in intensity caused
by
changes in the sweep
triggering
rate (sweep
duty
cycle).
Clockwise
rotation
increases the intensity and counterclock-
wise rotation decreases the intensity.
Focus
and Astigmatism Controls
The FOCUS
and
ASTIGMATISM controls
operate
in
con-
junction with each other to
allow
you to
obtain
a sharp,
clearly defined spot
or
trace.
To
adjust these controls:
1.
Adjust the INTENSITY control
for
the most pleasing level.
2.
Set the ASTIGMATISM control to midscale.
3.
Adjust the FOCUS control
for
sharpest detail.
4.
Adjust the ASTIGMATISM control
as
necessary
for
best
overall
focus.
Graticule 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 graticule 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.
Rotating the control clockwise increases the brightness
of
the
graticule markings and counterclockwise
rotation
decreases
the brightness.
NOTE
The
graticule
is
illuminated
only
when
operating
from
an
ac
line.
This
permits
longer
operation
when
on
batteries.
Positioning Controls
Two controls are used
with
the Type
321
A Oscilloscope
to
position the trace
or
spot
on
the screen.
The
HORIZONTAL
POSITION control moves the trace to
the
right
when
it
is
rotated
clockwise
and
to the left when it
is
rotated counterclockwise. This control has a positioning
range
of
approximately
15 divisions
with
the sweep
magnifier
off,
and
approximately
75
divisions
with
the sweep
magnifier
on.
The
HORIZONTAL
POSITION control
is
a combination
coarse/vernier
type
of
control. Built-in blacklash between
its
two
sections permits
30°
of
vernier adjustment
for
a given
coarse setting.
If
a
30
o
range
is
exceeded, the coarse
ad-
justment takes over to
provide
fast positioning
of
the trace.
The VERTICAL 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.
Intensity Modulation
The crt
display
of
the Type
321
A Oscilloscope can be in-
tensity
modulated
by
an
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
the beam from maximum intensity,
less
with
lower
intensity levels.
Negative-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 a useful
display,
the spot
formed by the electron beam
is
deflected
horizontally
at
a
known rate,
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 deflection
of
the
spot bears a definite relationship to time, and provides the
means
for
making time measurements from the screen, the
horizontal sweep
is
also known
as
the time base.
(See
Fig.
3-2).
The rate
at
which the spot
is
deflected across the screen
is
accurately controlled
by
the setting
of
the
TIME/DIV
con-
trol. The setting
of
the
TIME/DIV
control determines the
sweep rate, 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
Instructions-Type
321A
(SN
100-5999)
3-2
CRT
CONTROLS
FOCUS -Controls
sharpness
of
spot
or
trace.
tion with
focus.
VERTICAL CONTROLS
VERTICAL
POSITION
trace
vertically.
AC-DC-GND-Selects
either
AC
or
---H~illlll
1
DC
input
coupling.
The GND
posi-
tion connects
the
Vertical Amplifier
to
ground
but
does
not
ground
the
input
signal.
VOLTS/DIV
and
VARIABLE
-
Se-
lects vertical
deflection
factor
and
calibrator
signal.
INPUT -Terminal for
accepting
waveforms
to
be
displayed
on
crt.
CAL
OUT
500
MY-Terminal
pro-
vides
500-mv
square
wave
for
compensating
probe.
DC
SAL-Potentiometer
for
setting
de
balance
of
Vertical Amplifier.
INTENSITY-Controls
brightness
of
SCALE
ILLUM-Adjusts
brightness
of
graticule
markings
(when
oper-
ating
from
AC
line).
CONTROLS
HORIZONTAL
POSITION-Coarse-
vernier
type
of
control
that
posi-
tions
trace
horizontally.
regulated
1
0-volt
power
on
and
off. Also,
selects
charging
rate.
TIME/DIV
and
VARIABLE-Selects
~......;;~..,.,.,.....--
sweep
rate
and
external
horizontal
input.
EXT
HORIZ
INPUT-Terminal
for
external
horizontal
sig-
CONTROLS
SLOPE-Determines
whether
sweep
is
triggered
on
+
or
-
slope
of
triggering
signal.
AC-DC-Selects
AC
or
DC
coupling
for
triggering
signal.
ting
de
level
of
sweep
generator.
INPUT-Terminal
for
accepting
ex-
ternal
triggering
signal.
Fig.
3-1.
Functions
of
the
Type
321
A Oscilloscope
front-panel
controls.
®

r
r-
--!
I~
c. r
rP
r
;J
rJ
Voltage
--'
'-.J
~
I
Time-------+-
Fig.
3-2.
The oscilloscope plots
instantaneous
voltage
versus time
1
thereby
serving
both
as
a
voltmeter
and
a timer.
The Time
Base
has
19 accurately calibrated sweep rates
ranging from
.5
fLSec/div to
.5
sec/div. These calibrated
sweep rates are obtained when the VARIABLE (TIME/DIY)
• ·control
is
fully
clockwise
in
the CALIB position. The TIME/
DIY switch selects the calibrated sweep rates and can be
rotated 360
o
since there are no mechanical stops. The VARI-
ABLE
control permits you to
vary
the sweep rate continuously
between
.5
p.,sec/div and
approximately
1.5 sec/div.
All
sweep rates obtained with the VARIABLE control
in
any
position other than
fully
clockwise are uncalibrated.
Sweep
Magnifier
The sweep magnifier allows you to expand any two-
division portion
of
the displayed waveform to the full ten-
division
width
of
the graticule.
This
is
accomplished
by
first
using the
HORIZONTAL
POSITION control to move the por-
tion
of
the display you wish to expand to the center
of
the
graticule, then placing the 5 X
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 can then be observed
by
rotating the HORIZONTAL
POSITION control.
In
magnified sweep operation
1
the sweep rate indicated
by
the position
of
the TIME/DIY switch must be
divided
by
5 to obtain the actual time required
for
the spot
to
move
one division. For example
1
if
the TIME/DIY switch
is
set
to
5 MILL!
SEC
1
the actual time per division
is
5 milliseconds
divided
by
5
1
or
1 millisecond per division. The actual time-
per-division must be used for all time 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 internal 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
place the TIME/DIY switch
in
the
EXT
position. The hori-
zontal deflection factor
is
approximately
1
volt/
division with
the 5
X
MAG
on.
Operating
Instructions-Type
321A
(SN
100-5999)
TIME/DIV
Unmagnified
Waveform
SX
MAG
OFF
SX
MAG
ON
(pull!
-I-
I
--
--
I
I
1-r
I
I
I
I
I
I
I
l
--·
\
..
-
r-
I'' I
I
\
.f-,
--
~
\
\
\
\
\
\
'-
\
I
-r--
Magnified
Waveform
Fig.
3-3.
Operation
of
the
sweep
magnifier.
Sweep
Triggering
The oscilloscope display
is
formed
by
the repetitive sweep
of
the spot across the oscilloscope screen.
If
the sweeps are
allowed
to occur
at
random,
or
a rate unrelated
to
the input
waveform, the displayed waveform
will
be traced out
at
a
different
point
on the screen with each sweep. This
will
either cause the waveform to
drift
across the screen
or
to
be
indistinguishable.
In
most
cases
it
is
desirable
for
repetitive waveforms to
appear
stationary on the oscilloscope screen
so
that the
characteristics
of
the waveform can be examined
in
detail.
As
a necessary condition
for
this type
of
display, the start
of
the sweep must bear a definite, fixed-time relationship to
the observed waveform.
This
means
that
each sweep must
start
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 a definite time relationship
to the displayed waveform.
The waveform used to start the horizontal sweep
is
called
a
"triggering
signal" (whether
it
is
the waveform being ob-
served,
or
some other waveform). The
following
instructions
tell you how
to
select the triggering signal source.
Selecting
the
Triggering Source
In
preparing the Type
321
A Oscilloscope
for
triggered
operation
of
the sweep,
it
is
first necessary
to
select the
triggering signal source which
will
provide
the best display
for
the particular application. The sweep
can
be triggered
by
the displayed waveform,
or
by an externally derived
waveform. This selection
is
made
by
the setting
of
the INT-
EXT
switch
(see
Fig. 3-4).
Each
type
of
triggering
has certain
advantages
for
some applications.
Triggering from the displayed 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
Instructions-Type
321A
(SN
100-5999)
gering
is
convenient since no external triggering connections
are required. Satisfactory results are obtained in most
appli-
cations.
To
trigger
the sweep from some external waveform, con-
nect the
triggering
waveform to the (TRIGGERING) INPUT
connector and place the INT-EXT switch
in
the
EXT
position.
(External
triggering
provides definite advantages over in-
ternal
triggering
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
a signal
in
an external circuit
without
reset-
ting the oscilloscope triggering controls
for
each observation.
Also, time and phase relationships between 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 a circuit, the time relationship and phase
of
the waveforms
at
each point
in
the circuit are compared to
the input signal
by
the
display
presented on the oscilloscope
screen.
Selecting
the
Triggering Slope
The horizontal sweep can be triggered 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
triggering
waveform; when the
Displayed
Waveform
-
i....--
......___
INT
SLOPE
switch
is
in
the -position, the sweep
is
triggered on
the
falling
portion
of
the waveform
(see
Fig. 3-5).
In
many applications the
triggering
slope
is
not important
since triggering on either slope
will
provide
a display suitable
to the application.
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
at
the average
voltage
point
of
the
applied
waveform. Also, the sweep
runs
at
approxi-
mately a 50-cycle rate when no triggering signals are
ap-
plied; this produces a reference trace
or
baseline on the
screen. Automatic
triggering
can be used
with
both internal
and external triggering signals, but
for
most waveforms
it
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 the
triggering level
for
each observation. For this reason it
is
the mode
that
is
normally
used.
Other
modes are generally
used
only
for
special applications,
or
where stable trigger-
ing
is
not
attainable
in
the automatic mode.
External
Triggering
Waveform
EXT
--------1
I
NT-EXT
Switch
INPUT
Oscilloscope
Sweep-Starting
Circuits
Fig.
3-4
The
triggering
signal
is
selected
from
two
possible
sources
with
the
INT
-EXT
switch.
3-4
®
i :

i ~
®
SLOPE
l: SLOPE
Sweep Triggers
On - Slope
SLOPE
+
L: SLOPE
Sweep Triggers
On - Slope
Operating Instructions-Type 321A (SN 100-5999)
Waveforms obtained with the trig-
gering level control set in the
- region.
Waveforms obtained with the trig-
gering level control set in the
+ region.
Fig. 3-5. Effects on the oscilloscope display produced by + and - settings of the SLOPE and LEVEL controls.
3-5

Operating Instructions-Type 321A (SN 100-5999)
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 a general
rule, however, the ac mode
is unsatisfactory for triggering
with low amplitude waveforms at frequencies below approxi-
mately 15 cycles. This figure will vary depending upon the
amplitude and shape of the triggering waveform and should
not therefore be set as an absolute standard. Triggering at
frequenci~s below 15 cycles can be accomplished when
higher amplitude triggering signals are used.
In the ac mode, the triggering point depends on the
average voltage level of the triggering signals. If the trig-
gering signals occur at random, the average voltage level
will vary causing the triggering point to vary also. This shift
of the triggering point may be enough so that it is impossible
to maintain a stable display. In such cases you should use
the de mode.
De Mode
De mode triggering is obtained by setting the AC-DC
switch to the DC position. This mode of triggering is par-
ticularly useful in triggering from waveforms which are not
adaptable to the ac mode, such as random pulse trains or
very low-frequency waveforms. Random pulse trains pose
a special problem in the ac mode since the random occur-
rence of the input waveforms causes the average voltage
level to shift. This in turn may cause the triggering level to
shift to an unstable point. This problem is not 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 triggering point. For this reason,
you
may find it necessary to readjust the LEVEL control when
you change the vertical position
of the trace. To eliminate
this effect, you can
use the ac mode provided the triggering
signal is otherwise suitable for this mode of operation. In
the de mode, the de level of the external triggering signals
will also effect the triggering point. Generally, when the
triggering signal is small compared to its de level, the ac
mode should be used.
How to Set the Triggering Level
In the ac and de triggering modes, the LEVEL control
determines the
voltage level on the triggering waveform at
which the sweep is triggered. Using this control, the sweep
can be continuously triggered at any point on the waveform
so long as the slope of the waveform is great enough to
provide stable triggering. In the de mode, the sweep cannot
be triggered with any degree of stability at the top of a
square wave, for example, because the time that the voltage
remains constant is comparatively long. As a result, the
sweep triggers at random points along the top of the square
wave, producing considerable trace jitter.
You can
use the same method to set the LEVEL control for
either the ac or de mode. After selecting the triggering
slope, rotate the
LEVEL control fully counterclockwise to the
AUTO position. Then rotate the LEVEL control clockwise
until the sweep no longer triggers. Continue to rotate the
3-6
control in the clockwise direction until the sweep again trig-
gers and a stable
display is obtained. Further rotation 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 (Fig. 3-5}.
FREE-RUNNING OPERATION
With the Type 321 A, you can get a periodic, free-running
sweep, independent of any external 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 can then be used to posi-
tion the sweep or to establish a voltage reference line. The
difference between the traces produced in the AUTO position
and the FREE RUN position is the repetition rate. The repeti-
tion rate in the FREE RUN position is dependent upon the
setting of the timing switch. The repetition rate in the AUTO
position is fixed at approximately 50 cycles. At the faster
sweep rates, the trace in the AUTO position 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 can be either ac- or
de-coupled by placing the AC-DC-GND switch in the ap-
propriate AC or DC position. De coupling applies both the
ac and de components of the input signal to the vertical
amplifier circuit. This permits measurement of the de voltage
level as well as the amplitude of the ac component. It is
sometimes neither necessary nor desirable to display the de
component, however, and in such cases as coupling should
be used. This is accomplished by setting the AC-DC-GND
switch to AC. With ac coupling, a capacitor is placed in
series with the input connector to block the de 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 de zero reference. In this position the switch internally dis-
connects, but does not ground, the
applied signal to the
input connector.
Thus, the GND position eliminates the usual
need for externally grounding the (Vertical Amplifier} INPUT
connector of the Type 321 A or the probe tip to establish a
ground reference.
Deflection Factor
The electrical 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 vertically to trace out the waveform on
the screen of the crt. The VOLTS/DIY switch controls the
vertical deflection factor in accurately calibrated steps. The
VARIABLE control provides uncalibrated
variable deflection
factors between the fixed steps
of the VOLTS/DIY switch.
The VARIABLE control has 360o rotation range and a detent
position when the control
is set to CALIB.
®

NOTE
To
make
the
deflection
factor
equal
to
that
indi-
cated
by
the
VOLTS/DIY
switch,
set
the
VARIABLE
control
to
the
CALIB
detent
position.
De
Balance Adiustment
The need
for
adjustment
of
the DC
BAL
control
is
indi-
cated
by
a vertical shift
in
the position
of
the trace
as
the
VARIABLE (VOLTS/DIY) 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 (VOLTS/DIY) control back
and
forth,
and adjust the DC
BAL
control simultaneously until
the
trace position
is
no longer affected
by
rotation
of
the
VARIABLE control.
Input Signal Connections
Certain precautions must be observed when you are
con-
necting the oscilloscope
to
an
input
signal 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
waveforms containing
high-
or
extremely low-frequency components. For applica-
tions where you are observing low-level signals, shielded
cables should be used whenever possible,
with
the shield
connected to the chassis
of
both the oscilloscope
and
the
signal source. Unshielded input leads 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
as
possible.
Distortion
of
the input waveform
may
result if:
1.
Very low-frequency input signals are ac-coupled
to
the
oscilloscope.
2.
High-frequency waveforms are not
properly
terminated.
3.
The input waveform contains high-frequency components
which exceed the bandpass
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
cases
this loading effect
is
negligible; how-
ever,
in
some applications loading caused
by
the oscilloscope
may
materially
alter the results obtained.
In
such
cases
you
may wish to reduce the amount
of
loading
to a
negligible
amount through the
use
of
a probe.
Use
of
Probes
Occasionally connecting the input
of
an oscilloscope to
a signal source loads the source sufficiently to adversely
affect both the operation
of
the source and the waveform
displayed on the oscilloscope.
In
such
cases
an attenuator
®
Operating
Instructions-Type
321A
(SN
100-5999)
probe
may
be used
to
decrease both the capacitive and resis-
tive
loading
caused
by
the oscilloscope
to
a
negligible
value.
In
addition
to
providing
isolation
of
the oscilloscope from
the signal source, an
attenuator
probe
also decreases the
amplitude
of
the displayed
waveform
by
the attenuation
factor
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. Signal amplitudes, however, must be limited
to
the maximum
allowable
value
of
the probe used.
When
making
amplitude
measurements with an attenuator probe,
be sure to
multiply
the observed
amplitude
by
the attenua-
tion
of
the probe.
If
the waveform being displayed has
rapidly
rising
or
falling
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
point
of
measurement,
as
shown
in
Fig. 3-6.
Fig.
3-6.
Connecting
a
probe
to
the
input
signal
source.
Before using a
probe
you must check (and adjust
if
neces-
sary) the compensation
of
the probe to prevent distortion
of
the
applied
waveform. The probe
is
compensated
by
adjust-
ing the control located
in
the
body
of
the probe. Adjustment
of
the
probe
compensates
for
variations
in
input capacitance
from one instrument
to
another. To insure the accuracy
of
pulse and transient measurements, this adjustment should be
checked frequently.
To adjust 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 INT-EXT switch
to INT. Connect the
probe
tip to the CAL
OUT
500
MY
con-
nector.
Set
the
TIME/DIY
switch to
.5
MILLI
SEC
and adjust
the probe to obtain
flat
tops on the displayed square wave-
form
(see
Fig. 3-7.)
3-7

Operating
Instructions--Type
321A
(SN
100-5999)
Voltage
Measurements
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 same
although
the actual techniques
vary
somewhat
depending
on
the types
of
voltage
measurements, i.e., ac-component volt-
age
measurements,
or
instantaneous
voltage
measurements
with
respect to some reference potential.
Many
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 screen
as
possible
for
maximum 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
should be used
for
all
succeeding read-
ings. The VARIABLE (VOLTS/DIY) control must be in the
CALIB detent position.
Ac
Component
Voltage
Measurements
To
measure the
ac
component
of
a
waveform,
the AC-DC-
GND
switch should be set to the
AC
position.
In
this position
only
the ac components
of
the input
waveform
are
displayed
on the oscilloscope screen. However, when the ac component
of
the
input
waveform
is
very
low
in frequency, it
will
be
necessary
for
you
to
make
voltage
measurements
with
the
AC-DC-GND
switch in the DC position.
To
make a peak-to-peak
voltage
measurement on the ac
component
of
a
waveform,
perform the
following
steps
(see
Fig. 3-8).
Incorrect
Adjusted
Correctly
1.
With
the
aid
of
the graticule, measure the vertical dis-
tance in divisions from the positive peak
to
the negative
peak.
2.
Multiply
the setting
of
the
VOLTS/DIY
control
by
the dis-
tance measured to
obtain
the
indicated
voltage.
3.
Multiply
the indicated
voltage
by
the attenuation
factor
of
the
probe
you
are
using to
obtain
the true peak-to-peak
voltage.
As an example
of
this method, assume
that
using the
P6006
Probe
and
a deflection
factor
of
1
volt
per
division,
you measure a vertical distance between peaks
of
4 divisions.
In
this case, then, 4 divisions
multiplied
by
1
volt
per
divi-
sion gives you an indicated
voltage
of
4 volts peak-to-peak.
The indicated
voltage
multiplied
by
the probe's attenuation
factor
of
1
0 then gives you the true peak-to-peak
amplitude
of
40 volts.
When
sinusoidal waveforms are measured, the peak-to-
peak
voltage
obtained
can be converted
to
peak, rms,
or
average
voltage
through
use
of
standard conversion factors.
Instantaneous
Voltage
Measurements
The method used to measure instantaneous voltages
is
virtually
identical to the method described previously
for
the measurement
of
the ac components
of
a
waveform.
How-
ever,
for
instantaneous
voltage
measurements the AC-DC-
GND
switch must be placed in the DC position. Also, since
instantaneous voltages are measured
with
respect to some
potential (usually ground), a reference line must be
established on the oscilloscope screen which corresponds
to
that
potential. If,
for
example,
voltage
measurements are to
be made
with
respect to
+
100 volts, the reference line
would
correspond to
+
100 volts.
In
the
following
procedure a
method
is
presented
for
establishing this reference line
at
ground, since measurements
with
respect
to
ground are the
Incorrect
P6006
Probe-Hold
probe
barrel
and
loosen
locking
sleeve
several
turns. Hold
probe
base
while
adujsting
probe
barrel
for
flat-top
square
waves.
Hold
probe
barrel
and
carefully
tighten
locking
sleeve.
Fig.
3-7.
The
probe
is
adjusted
to
obtain
an
undistored
presentation
of
the
calibrator
squarewave.
3-8
®