Tektronix 7B10 Instruction Manual page 16

Operating
Instructions-
7B10
TRIGGERING FUNCTIONS
Perform
the following
procedure
to obtain a triggered
sweep and
to
demonstrate
the functions
of
the
related
controls:
1
.
Obtain
a display as described
in
the preceding Normal
Sweep
procedure.
2.
Turn
the
LEVEL
control
fully
counterclockwise
to
obtain
a
free-running
sweep.
3.
Slowly
turn the
HOLD
OFF
control
clockwise and
note
that a stable display can be obtained
at
several positions
of
the
HOLD
OFF
control
Return the
HOLD
OFF
control
to
the
fully
counterclockwise (MIN)
position.
NOTE
The
HOLD
OFF
control varies the
sweep
hold-
off
time which
effectively
changes
the
repetition-rate of the horizontal
sweep
signal.
However,
its
primary
function
is
to
obtain a
stable display of
complex waveforms which
are otherwise
difficult to trigger.
4.
Press the
AC,
AC
HF
REJ,
and
DC COUPLING
buttons
for
both the +
and
-
positions
of
the
SLOPE
switch
and
check
for a stable display
(LEVEL
control
may
be
adjusted,
if
necessary,
to
obtain a stable display).
5.
Apply
the
0.4-volt,
1
kilohertz signal
from
the
mainframe
calibrator
to
the amplifier
unit
and
to
the
EXT
TRIG
IN connector.
6.
Press
the
EXT
SOURCE
button
and
set
the
amplifier
unit
deflection factor
for a 4-division display.
7.
Press the AC,
AC
HF
REJ,
and
DC COUPLING
buttons
for
both the +
and
-
positions
of
the
SLOPE
switch
and
check
for
a stable display
(LEVEL
control
may
be
adjusted,
if
necessary).
8.
Press the
AC
COUPLING,
INT
SOURCE,
and
NORM
MODE
buttons. Adjust the
LEVEL
control
for a stable
display
9.
Press the
AUTO
MODE
button
and
adjust the
LEVEL
control for a
free-running
display.
10. Press the
NORM MODE
button and check
for
no
display.
11. Adjust the
LEVEL
control
for a stable display
and
press the
SINGLE
SWP MODE
button.
12.
Note
that
one
trace occurs
when
the
SINGLE
SWP
button
is
pressed
again.
13.
Disconnect
the
mainframe
calibrator signal
from
the
amplifier unit input
and
press the
SINGLE
SWP
button.
Check
for
no
display
and
note
that the
READY
indicator
is
lit.
14.
Note
that
one
trace occurs
and
that
the
READY
indicator
extinguishes
when
the
mainframe
calibrator
signal
is
reconnected
to
the
amplifier unit input.
DETAILED
OPERATING
INFORMATION
TRIGGERING SWITCH
LOGIC
The
MODE, COUPLING,
and
SOURCE
push
buttons
of
the
TRIGGERING
switches
are
arranged
in a
sequence which
places the most-often
used
position
at
the top
of
each
vertical
row
of
push
buttons.
With
this
arrangement,
a
stable display
can
usually
be obtained
by pressing the top
push
buttons:
AUTO,
AC,
INT
When
an adequate
trigger
signal
is
applied
and
the
LEVEL
control
is
correctly
set,
the
unit
is
triggered as indicated
by the illuminated
TRIG'D
light.
If
the
TRIG'D
light
is
not on, the
LEVEL
control
is
either
at
a setting
outside the
range
of
the
trigger signal
applied
to this unit
from
the
vertical
unit,
the
trigger
signal
amplitude
is
inadequate,
or
its
frequency
is
below
the lower frequency
limit
of
the
AC
COUPLING
switch
position.
If
the desired
display
is
not
obtained with these buttons
pushed
in,
other selections
must be made.
Refer to
the following discussions
or the
instruction
manuals
for
the associated oscilloscope
mainframe and
vertical
unit(s) for
more
information.
TRIGGERING
MODE
The
MODE
push-button switches
select
the
mode
in
which
the
sweep
is
triggered.
Auto
The
AUTO
MODE
provides
a
triggered display with the
correct setting
of
the
LEVEL
control
whenever
an
adequate
trigger
signal
is
applied (see Trigger Level
discussions).
The TRIG'D
light
indicates
when
the
display
is
triggered.
When
the trigger repetition rate
is
outside the frequency
range selected by the
COUPLING
switch
or
the
trigger
signal
is
inadequate, the
sweep
free
runs
at
the
rate
indicated
by the
TIME/DIV
switch (TRIG'D
indicator
off).
An
adequate
trigger
signal
ends
the free-running
condition
and
a triggered display
is
presented.
The sweep
also free
runs
at
the
rate indicated
by the
TIME/DIV
switch
when
the
LEVEL
control
is
at
a setting outside the
amplitude range
of
the
trigger signal.
This type
of free-
running
display
is
useful
when
it
is
desired
to
measure
only the peak-to-peak amplitude
of a signal
without
observing
the
waveshape
(such
as
bandwidth
measurements).
HF Sync
The HF
SYNC mode
provides
a triggered display
with the
correct setting
of
the
LEVEL
control
whenever
a
high
frequency, (1(^
MHz
or higher)
low amplitude
signal
is
applied.
This
mode
is
useful
when
the incoming
signal
is
too small
to
produce
stable triggering
in
the
AUTO
or
NORMAL
modes. The
HF
SYNC
mode
increases
trigger
sensitivity
and
provides automatic
trigger amplifier
centering
for
optimum
triggering
under these
conditions.
2-4