Hardware Reference
In-Depth Information
between 10 KB and 100 KB samples per second. Resolution is usually limited
to either 8- or 12-bits (corresponding to 256 and 4096 discrete voltage levels,
respectively).
Low-cost DSO may be either single- or dual-channel units and, by virtue of
their low cost and simplicity, they are ideal for educational purposes as well
as basic measurements. Most low-cost DSO provide all of the functionality
associated with a conventional 'scope but with many additional software-driven
features at a fraction of the price of a comparable conventional test instrument.
That said, there are two important limitations of low-cost DSO:
1
Their bandwidth is generally limited so that they are only suitable for
examining low-frequency and audio signals.
2
Their resolution is generally limited to 8 bits or 256 discrete steps of
voltage.
A typical specification for a low-cost DSO is:
Sampling rate:
20 KB samples per second
Resolution:
8 bits
Number of channels:
1
Low-cost DSO frequently require no external power supply as they draw their
power from the parallel port or USB port of a PC. This makes them ideal for
use with laptop computers without the need for a mains supply.
High-speed DSO
High-speed DSO are usually dual-channel instruments that are designed to
replace conventional general-purpose oscilloscopes (bit with the added advan-
tage that captured data can be stored for subsequent processing and analysis).
These instruments have all the features associated with a conventional 'scope
including trigger selection,
timebase and voltage ranges,
and an ability to
operate in X-Y mode.
Additional features available with a computer-based instrument that are not
usually available from conventional benchtop 'scopes include the ability to cap-
ture transient signals (as with a storage 'scope) and save waveforms for future
analysis. The ability to analyse a signal in terms of its frequency spectrum is
yet another feature that is only possible with a DSO (more of this later).
A typical specification for a high-speed DSO is:
Sampling rate:
50 MB samples per second
Resolution:
8 bits
Number of channels:
2
Autoranging
is another very useful feature that is often provided with a DSO.
If you regularly use a conventional 'scope for a variety of measurements you
will know only too well how many times you need to make adjustments to the
