The
terms
described
in this
section
may come
up in
your
discussions
about
oscilloscope
performance.
Understanding
these
terms
will
help you
evaluate
and
compare
your
oscilloscope
with
other
models.
Bandwidth
The
bandwidth
specification
tells
you the
frequency
range
the
oscilloscope
accurately
measures.
As
signal
frequency
increases,
the
capability
of the
oscilloscope
to
accurately
respond
decreases.
By
convention,
the
bandwidth
tells
you the
frequency
at which
the
displayed
signal
reduces
to 70.7%
of the
applied
sine
wave
signal.
(This
70.7%
point is
referred
to as
the "-3
dB
point,"
a term
based on
a
logarithmic
scale.)
Rise
Time
Rise
time is
another
way of
describing
the
useful
frequency
range of
an
oscilloscope.
Rise
time may
be a
more
appropriate
performance
consideration
when you
expect
to
measure
pulses
and
steps.
An
oscilloscope
cannot
accurately
display
pulses
with
rise
times
faster
than the
specified
rise
time of
the
oscilloscope.
Vertical
Sensitivity
The
vertical
sensitivity
indicates
how much
the
vertical
amplifier
can
amplify
a weak
signal.
Vertical
sensitivity
is
usually
given in
millivolts
(mV) per
division.
The
smallest
voltage
a
general
purpose
oscilloscope
can
detect
is
typically
about 2
mV per
vertical
screen
division.
Sweep
Speed
For
analog
oscilloscopes,
this
specification
indicates
how fast
the
trace
can
sweep
across
the
screen,
allowing
you to
see fine
details.
The
fastest
sweep
speed of
an
oscilloscope
is
usually
given in
nanoseconds/div.
Gain
Accuracy
The gain
accuracy
indicates
how
accurately
the
vertical
system
attenuates
or
amplifies
a
signal.
This is
usually
listed
as a
percentage
error.
Time
Base or
Horizontal
Accuracy
The time
base or
horizontal
accuracy
indicates
how
accurately
the
horizontal
system
displays
the
timing
of a
signal.
This is
usually
listed
as a
percentage
error.
Sample
Rate
On
digital
oscilloscopes,
the
sampling
rate
indicates
how many
samples
per
second
the ADC
(and
therefore
the
oscilloscope)can
acquire.
Maximum
sample
rates
are
usually
given in
megasamples
per
second
(MS/s).
The
faster
the
oscilloscope
can
sample,
the more
accurately
it can
represent
fine
details
in a
fast
signal.
The
minimum
sample
rate may
also be
important
if you
need to
look at
slowly
changing
signals
over
long
periods
of time.
Typically,
the
sample
rate
changes
with
changes
made to
the
sec/div
control
to
maintain
a
constant
number
of
waveform
points
in the
waveform
record.
ADC
Resolution
(Or
Vertical
Resolution)
The
resolution,
in bits,
of the
ADC (and
therefore
the
digital
oscilloscope)
indicates
how
precisely
it can
turn
input
voltages
into
digital
values.
Calculation
techniques
can
improve
the
effective
resolution.
Record
Length
The
record
length
of a
digital
oscilloscope
indicates
how many
waveform
points
the
oscilloscope
is able
to
acquire
for one
waveform
record.
Some
digital
oscilloscopes
let you
adjust
the
record
length.
The
maximum
record
length
depends
on the
amount
of
memory
in your
oscilloscope.
Since
the
oscilloscope
can only
store a
finite
number
of
waveform
points,
there is
a
trade-off
between
record
detail
and
record
length.
You can
acquire
either a
detailed
picture
of a
signal
for a
short
period
of time
(the
oscilloscope
"fills
up" on
waveform
points
quickly)
or a
less
detailed
picture
for a
longer
period
of time.
Some
oscilloscopes
let you
add more
memory
to
increase
the
record
length
for
special
applications.
