Tektronix 543B Instruction Manual page 10

Operating
Instructions
—
Type
543B/RM543B
trigger signal to the
TRIGGER INPUT
connector.
External
triggering
is
often used
when
slgnol treeing
in
amplifiers,
phase-shift
networks,
end
wove-shoping
circuits.
The
signol
from 0 single point
in
the circuit
con
be
used os
on
exiernol
trigger signol,
With
this
orrongement.
it is
possible
to
observe
the polarity,
shaping ood/or
omplilicotion
of
a
signol at
vorious points through the
circuit
without
resetting
the triggering controls for
eoch
new
disploy.
Selecting Triggering
Mode
Four
means
of trigger
coupling are avoilobio with the
TRIGGERING
MODE
switch.
The
different
coupling
posi-
tions permit
you
to
accept
or reject certain
frequency com-
ponents
of the triggering signal.
With
the switch set ot
AC,
the time bose con
be
triggered
with
all
frequency
components
of
the triggering signal
within the trigger amplifier faandposs, including
dc
levels.
With
the switch set of
AC
LF
REJ, dc
ond low-frequency
signals
(below about 17
kc)
ore
rejected
or oflenualed. Thus,
the trigger circuit will
respond
best to the
higher-frequency
components
of
the triggering signal.
With
the switch
set to
AUTO,
proper triggering
auto-
maticolly takes place providing fhot the
sigrtol
woveform
is
comparatively simple and approximately
symmetrical.
With
no trigger signal, or with
o lower
repetition
rote,
the trigger
circuit free
runs at
approximotely 40cp$ ond
triggers
the
time base
at
this
rote, providing
a
reference
Iroce.
In
general, use
AC
coupling.
However,
it
will
be nccessory
to use
DC
coupling
for
very iow-frequoncy
slgnols.
When
line-frequency
hum
is
mixed with the
triggering signal,
it
is
best to
use
AC
LF
REJ coupling so
that triggering takes
place only on the signal of
interest (H
the signol of
interest
contains
frequency components above about
17kc)-
The
AC
LF REJ position
is
also useful
when
triggering
internolly
from
mulfifrace plug-in
units
operated
in
the
alternate dual-trace
mode.
AC
LF REJ coupling hos
o
foster
recovery time
when
subjected
to
the alternate
dc
levels
from
the multitrace plug-in
unit.
Selecting Trigger
Slope
The
TRIGGER SLOPE
switch determines
whether
the
trigger-
ing
circuit
responds
on the
rising (+
setting)
or the falling
(
—
setting)
portion of the triggering
signol.
When
severol
cycles
of
a
signal
appear
In
the display, the setting of the
TRIGGER SLOPE
switch
will
probably be
unimportant.
How-
over,
if
you wish
to
look
of
only o certoio portion of a
cycle,
the
TRIGGER SLOPE
switch will
help
start
the display
on
the
desired slope
of
the input signal. Fig.
2-3
iliostrotes
the
effect
of both the
TRIGGER SLOPE and
TRIGGERING
LEVEL
controls.
Setting Stability
Control
In
nearly
oil
triggering appllco'ions, sotisfoctory opero-
tion
can be
obtoined
with the
STABILITY
control
in
the
PRESET
(fully
counterclockwise) position.
The PRESET
posi-
tion
has tho
advantoge of requiring
no
further
odjuslment
of
the
STABILITY
control
when
switching
from one triggering
signal
to
another.
However,
if
stable
triggering
becomes
difficult
with
the
STABILITY
control
at
PRESET,
It
will
be
necessary
to adjust the control for
proper
triggering.
To
adjust the STABILITY
control,
place
the
TRIGGERING
LEVEL
control
in
the fully
counterclockwise
position, then turn the
STABILITY
control
slowly clockwise
until
a trace
appears on
the
crt.
The
correct setting
is
obtoined by
turning the control
counterclockwise
three to
five
degrees from
the point
where
the trace
appears.
Setting
Triggering
Level
The
TRIGGERING
LEVEL
control
determines the
amplitude
point
on
the signal
where
triggering occurs.
The
trigger
circuit
is
most
sensitive to
ac triggering signals
with the
TRIGGERING
LEVEL
control
set
neor zero.
Moving
the
TRIGGERING
LEVEL control
in
the
-F
(plus)
direction
causes the trigger
circuit
to
respond
at
some
higher
positive
amplitude on
the triggering
signal.
Moving
the
TRIGGERING
LEVEL
control in
fhc
(minus) direction
causes the trigger
circuit
to
respond
at
some higher negotive
amplitude on
the
triggering signal.
Selecting
Time/Cm (Sweep
Rate)
The
TIME/CM
and
HORIZONTAL
DISPLAY
switches con-
trol
sweep
rote.
The
TIME/CM
and
HORIZONTAL
DISPLAY
switches allow
you
to
view
on
applied signol at
a wide
variety of
cali-
brated
sweep
rates.
When
making
time measurements
from
the
crt,
be sure the
VARIABLE
control
Is
set
to
CALIBRATED,
When
the
HORIZONTAL
DISPLAY
switch
is
set to
NORMAL
(XI),
the
TIME/CM
switch indicates the
true
sweep
rate.
However,
with the
HORIZONTAL
DISPLAY
switch
set
to
o sweep
magnified
position,
the
setting of
the
TIME/CM
switch must be
divided by
the mognified
amount
to
determine
the
true
sweep
rate.
For
exomple, assume
that
the
TIME/CM
switch
is
set ot
1
mSEC
ond
the
HORI-
ZONTAL
DISPLAY
switch
is
set to
X5.
In this
cose, the
true
sweep
rate
would
be
I
(msec) divided by 5 (mognified
amount);
resu;tir>g in
a displayed
sweep
rate of 0.2
msec/
div.
Rg.
2-4
iilustrotes
how
to
make
time
measurements
from the groticule.
2-4
®T