Use the
vertical
controls
to
position
and
scale
the
waveform
vertically.
Your
oscilloscope
also has
controls
for
setting
the
input
coupling
and
other
signal
conditioning,
described
in this
section.
Following
Figure
shows a
typical
front
panel
and
on-screen
menus
for the
vertical
controls.
Vertical
Controls
Position
and
Volts
per
Division
The
vertical
position
control
lets you
move the
waveform
up or
down to
exactly
where
you want
it on
the
screen.
The
volts
per
division
(usually
written
volts/div)
setting
varies
the size
of the
waveform
on the
screen.A
good
general
purpose
oscilloscope
can
accurately
display
signal
levels
from
about 4
millivolts
to 40
volts.
The
volts/div
setting
is a
scale
factor.
For
example,
if the
volts/div
setting
is 5
volts,
then
each of
the
eight
vertical
divisions
represents
5 volts
and the
entire
screen
can show
40 volts
from
bottom
to top
(assuming
a
graticule
with
eight
major
divisions).
If the
setting
is 0.5
volts/div,
the
screen
can
display
4 volts
from
bottom
to top,
and so
on. The
maximum
voltage
you can
display
on the
screen
is the
volts/div
setting
times
the
number
of
vertical
divisions.
(Recall
that the
probe
you use,
1X or
10X,
also
influences
the
scale
factor.
You must
divide
the
volts/div
scale by
the
attenuation
factor
of the
probe if
the
oscilloscope
does not
do it
for
you.)
Often
the
volts/div
scale
has
either a
variable
gain or
a fine
gain
control
for
scaling
a
displayed
signal
to a
certain
number
of
divisions.
Use this
control
to take
rise
time
measurements.
Input
Coupling
Coupling
means
the
method
used to
connect
an
electrical
signal
from one
circuit
to
another.
In this
case,
the
input
coupling
is the
connection
from
your
test
circuit
to the
oscilloscope.
The
coupling
can be
set to
DC, AC,
or
ground.
DC
coupling
shows
all of
an input
signal.
AC
coupling
blocks
the DC
component
of a
signal
so that
you see
the
waveform
centered
at zero
volts.
Following
Diagram
illustrates
this
difference.
The AC
coupling
setting
is handy
when the
entire
signal
(alternating
plus
constant
components)
is too
large
for the
volts/div
setting.
AC
and DC
Input
Coupling
The
ground
setting
disconnects
the
input
signal
from the
vertical
system,
which
lets you
see
where
zero
volts is
on the
screen.
With
grounded
input
coupling
and auto
trigger
mode,
you see
a
horizontal
line on
the
screen
that
represents
zero
volts.
Switching
from DC
to
ground
and back
again is
a handy
way of
measuring
signal
voltage
levels
with
respect
to
ground.
Bandwidth
Limit
Most
oscilloscopes
have a
circuit
that
limits
the
bandwidth
of the
oscilloscope.
By
limiting
the
bandwidth,
you
reduce
the
noise
that
sometimes
appears
on the
displayed
waveform,
providing
you with
a more
defined
signal
display.
Channel
Invert
Most
oscilloscopes
have an
invert
function
that
allows
you to
display
a signal
"upside-down."
That is,
with low
voltage
at the
top of
the
screen
and high
voltage
at the
bottom.
Alternate
and Chop
Display
On
analog
scopes,
multiple
channels
are
displayed
using
either
an
alternate
or chop
mode.
(Digital
oscilloscopes
do not
normally
use chop
or
alternate
mode.)
Alternate
mode
draws
each
channel
alternately
- the
oscilloscope
completes
one
sweep on
channel
1, then
one
sweep on
channel
2, a
second
sweep on
channel
1, and
so on.
Use this
mode
with
medium-
to
high-speed
signals,
when the
sec/div
scale is
set to
0.5 ms
or
faster.
Chop
mode
causes
the
oscilloscope
to draw
small
parts of
each
signal
by
switching
back and
forth
between
them.
The
switching
rate is
too fast
for you
to
notice,
so the
waveform
looks
whole.
You
typically
use this
mode
with
slow
signals
requiring
sweep
speeds
of 1 ms
per
division
or less.
Following
Figure
shows
the
difference
between
the two
modes.
It is
often
useful
to view
the
signal
both
ways, to
make
sure you
have the
best
view.
Multi-Channel
Display
Modes
Math
Operations
Your
oscilloscope
may also
have
operations
to allow
you to
add
waveforms
together,
creating
a new
waveform
display.
Analog
oscilloscopes
combine
the
signals
while
digital
oscilloscopes
mathematically
create
new
waveforms.
Subtracting
waveforms
is
another
math
operation.
Subtraction
with
analog
oscilloscopes
is
possible
by using
the
channel
invert
function
on one
signal
and then
use the
add
operation.
Digital
oscilloscopes
typically
have a
subtraction
operation
available.
Following
Figure
illustrates
a third
waveform
created
by
adding
two
different
signals
together.
