Position
and
Seconds
per
Division
The
horizontal
position
control
moves
the
waveform
from
left and
right to
exactly
where
you want
it on
the
screen.
The
seconds
per
division
(usually
written
as
sec/div)
setting
lets you
select
the rate
at which
the
waveform
is drawn
across
the
screen
(also
known as
the time
base
setting
or sweep
speed).
This
setting
is a
scale
factor.
For
example,
if the
setting
is 1 ms,
each
horizontal
division
represents
1 ms and
the
total
screen
width
represents
10 ms
(ten
divisions).
Changing
the
sec/div
setting
lets you
look at
longer
or
shorter
time
intervals
of the
input
signal.
As
with the
vertical
volts/div
scale,
the
horizontal
sec/div
scale
may have
variable
timing,
allowing
you to
set the
horizontal
time
scale in
between
the
discrete
settings.
Time
Base
Selections
Your
oscilloscope
has a
time
base
usually
referred
to as
the main
time
base and
it is
probably
the most
useful.
Many
oscilloscopes
have
what is
called a
delayed
time
base - a
time
base
sweep
that
starts
after a
pre-determined
time
from the
start of
the main
time
base
sweep.
Using a
delayed
time
base
sweep
allows
you to
see
events
more
clearly
or even
see
events
not
visible
with
just the
main
time
base
sweep.
The
delayed
time
base
requires
the
setting
of a
delay
time and
possibly
the use
of
delayed
trigger
modes
and
other
settings
not
described
in this
book.
Refer to
the
manual
supplied
with
your
oscilloscope
for
information
on how
to use
these
features.
Trigger
Position
The
trigger
position
control
may be
located
in the
horizontal
control
section
of your
oscilloscope.
It
actually
represents
"the
horizontal
position
of the
trigger
in the
waveform
record."
Horizontal
trigger
position
control
is only
available
on
digital
oscilloscopes.
Varying
the
horizontal
trigger
position
allows
you to
capture
what a
signal
did
before
a
trigger
event
(called
pretrigger
viewing).
Digital
oscilloscopes
can
provide
pretrigger
viewing
because
they
constantly
process
the
input
signal
whether
a
trigger
has been
received
or not.
A steady
stream
of data
flows
through
the
oscilloscope;
the
trigger
merely
tells
the
oscilloscope
to save
the
present
data in
memory.
In
contrast,
analog
oscilloscopes
only
display
the
signal
after
receiving
the
trigger.
Pretrigger
viewing
is a
valuable
troubleshooting
aid. For
example,
if a
problem
occurs
intermittently,
you can
trigger
on the
problem,
record
the
events
that led
up to it
and,
possibly,
find the
cause.
Magnification
Your
oscilloscope
may have
special
horizontal
magnification
settings
that let
you
display
a
magnified
section
of the
waveform
on-screen.
XY
Mode
Most
oscilloscopes
have the
capability
of
displaying
a second
channel
signal
along
the
X-axis
(instead
of
time).
This is
called
XY mode
