Tektronix 7B10 Instruction Manual page 17

Operating Instructions—
7B 10
Normal
The
NORM MODE
provides
a triggered display
with the
correct settings
of
the
LEVEL
control
whenever
an
adequate
trigger
signal
is
applied.
The
TRIC'D
light
indicates
when
the display
is
triggered.
The
normal
trigger
mode
must
be
used
to
produce
triggered displays
with
trigger repetition rates
below
about
30
hertz.
When
the
TRIC'D
light
is
off,
no
trace
is
displayed.
Single
Sweep
When
the signal
to
be displayed
is
not
repetitive or
varies
in
amplitude,
waveshape,
or repetition
rate, a
conventional
repetitive type display
may
produce an
unstable presentation. Linder
these circumstances,
a
stable display
can
often
be obtained
by using the
single-
sweep
feature
of this
unit.
The
single-sweep
mode
is
also
useful
to
photograph
non-repetitive
or
unstable
displays.
To
obtain
a
single-sweep
display
of
a repetitive signal,
first
obtain the best possible display
in
the
NORM
MODE.
Then, without
changing
the other
TRICCERINC
controls,
press the
SINCLE
SWP
RESET
button.
A
single trace
is
presented each time
this
button
is
pressed. Further
sweeps cannot be presented
until
the
SINCLE
SWP
RESET
button
is
pressed
again.
If
the displayed signal
is
a
complex waveform composed
of
varying amplitude
pulses,
successive single-sweep
displays
may
not
start at
the
same
point
on
the
waveform. To
avoid confusion
due
to
the
crt
persistence,
allow the
display to
disappear
before pressing the
SINCLE
SWP
RESET
button
again.
At
fast
sweep
rates,
it
may
be
difficult to
view
the single-
sweep
display.
The
apparent
trace
intensity
can be
increased by reducing the ambient
light level
or by using
a
viewing hood
as
recommended
in
the
mainframe
instruction
manual.
When
using the single-sweep
mode
to
photograph
waveforms, the
graticule
may
have
to
be photographed
separately
in
the
normal manner
to
prevent
over
exposing
the
film.
Be
sure the
camera system
is
well
protected against stray
light,
or operate the system
in
a
darkened room.
For
repetitive
waveforms,
press the
SINCLE
SWP
RESET
button only once
for
each
waveform
unless the signal
is
completely symmetrical. Otherwise,
multiple
waveforms
may
appear on
the
film
For
random
signals,
the lens can be
left
open
until
the signal triggers
the
unit.
Further information
on
photographic techniques
is
given
in
the appropriate
camera
instruction manual.
TRIGGERING COUPLING
The TRICCERINC COUPLINC
push
buttons
select
the
method
in
which
the
trigger signal
is
connected
to
the
trigger circuits.
Each
position permits selection
or
rejection of
some
frequency
components
of
the
signal
which
triggers the
sweep.
Alternating Current
AC
COUPLINC
blocks the dc
component
of
the
trigger
signal.
Signals with low-frequency components below
about
30
hertz are
attenuated.
In
general,
AC COUPLINC
can
be
used
for
most
applications.
However,
if
the
signal
contains
unwanted
frequency components
or
if
the
sweep
is
to
be
triggered
at
a
low
repetition rate or dc
level,
one
of
the other
COUPLINC
switch positions
will
provide
a better display.
Alternating Current
Low
Frequency
Rejection
AC
LF
REJ COUPLINC
rejects dc,
and
attenuates low-
frequency
trigger signals
below
about
50
kilohertz.
Therefore, the
sweep
is
triggered only
by the higher-
frequency
components
of
the
trigger signal.
This
position
is
particularly
useful
for
providing stable
triggering
if
the
trigger signal
contains line-frequency components.
Also,
the
AC
LF REJ
position provides the best alternate-mode
vertical
displays
at
fast
sweep
rates
when
comparing two
or
more
unrelated
signals.
Alternating
Current High Frequency
Rejection
AC
HF REJ COUPLING
passes
all
low-frequency
signals
between
about
30
hertz
and 30
kilohertz.
Dc
is
rejected
and
signals outside the above range
are attenuated.
When
triggering
from complex waveforms,
this position
is
useful
to
provide
a
stable display
of
the low-frequency
components.
Direct
Current
DC COUPLING
can be used
to
provide stable triggering
from low-frequency
signals
which would
be attenuated
in
the other
COUPLING
switch
positions.
DC COUPLING
can be used
to trigger the
sweep when
the
trigger signal
reaches
a dc
level set
by the
LEVEL
control.
When
using
internal triggering,
the
setting
of
the
vertical unit position
control affects the
triggering point.
TRIGGERING
SOURCE
The
TRIGGERING
SOURCE
push
buttons
select
the
source
of the trigger signal
which
is
connected
to
the
trigger
circuits.
Internal
The
INT
position
connects the
trigger signal
from
the
vertical plug-in
unit.
Further selection
of
the
internal
trigger signal
may
be provided by the
vertical plug-in
unit
or
by the mainframe; see the
instruction
manuals
for
these
instruments
for
more
information. For most
applications,
the
internal
source can be
used.
However,
some
applications require
special triggering
which
cannot be
obtained
in
the INT
position.
In
such
cases, the
LINE
or
EXT
positions of
the
SOURCE
switches must
be
used.
Line
The LINE
position
connects
a
sample
of
the power-line
voltage
from
the
mainframe
to
the
trigger
circuit.
Line
triggering
is
useful
when
the input
signal
is
time-related
(multiple or submultiple)
to
the
line
frequency.
It
is
also
useful for providing a stable display
of a line-frequency
component
in a
complex waveform.
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