Specifications

19
Memory depth
As we mentioned earlier, a
digital oscilloscope uses an A/D
(analog-to-digital) converter to
digitize the input waveform. The
digitized data is then stored in
the oscilloscope’s high-speed
memory. Memory depth refers to
exactly how many records and,
therefore, what length of time can
be stored.
Memory depth plays an
important role in the sampling
rate of an oscilloscope. In an
ideal world, the sampling rate
would remain constant no matter
what the settings were on an
oscilloscope. However, this kind
of an oscilloscope would require a
huge amount of memory at small
time/division settings and would
have a price that would severely
limit the number of customers
that could afford it. Instead,
the sampling rate decreases as
you increase the range of time.
Memory depth is important
Important Oscilloscope Performance Properties (continued)
Memory depth
because the more memory depth
an oscilloscope has, the more
time you can spend capturing
waveforms at full sampling speed.
Mathematically, this can be
seen by:
Memory depth =
(sample rate)(time across display)
So, if you are interested in
looking at long periods of time
with high resolution between
points, you will need deep
memory. It is also important to
check the performance of the
oscilloscope when it is in the
deepest memory depth setting.
Scopes usually have a severe
drop in performance in this mode
and, therefore, many engineers
only use deep memory when it is
essential for their purposes.
To learn more about oscilloscope
memory depth, see Application
Note 1569, Demystifying Deep
Memory Oscilloscopes.
Oscilloscope Fundamentals