Hardware Reference
In-Depth Information
Instrument connection
Comments
Notes
IEEE-488 (via suitable
Suitable for comple ATE set-ups and
See Chapter 8 for
controller card)
test stands (can be limited in speed).
further information.
Firewire and optical
Potential for future high-speed
connections
instrumentation applications.
PCMCIA
A future solution for laptop computers
in field-service applications?
Digital storage
oscilloscopes
Probably the most well-known computer-based test instrument is the digital
storage oscilloscope (DSO). Because of the processing power available from
the PC coupled with the mass storage capability, a computer-based DSO is
able to provide a variety of additional functions, such as spectrum analysis and
digital display of both frequency and voltage. In addition, the ability to save
waveforms and measurements for future analysis, or for comparison purposes
can be extremely valuable, particularly where evidence of conformance with
standards or specifications is required.
Unlike a conventional oscilloscope which is primarily intended for waveform
display, a computer-based digital storage oscilloscope (DSO) effectively com-
bines several test instruments in one single package. The functions generally
available from a DSO include:
•
waveform display;
•
precise time and voltage measurement (using adjustable cursors);
•
digital display of voltage;
•
digital display of frequency and/or periodic time;
•
frequency spectrum display and analysis;
•
data logging (i.e. storage of waveform data for later analysis);
•
ability to save/print waveforms and other information in graphical format
(e.g. as .jpg or .bmp files).
The DSO comprises an external hardware unit which is connected to the PC
by means of either a conventional 25-pin parallel port connector or by means
of a serial USB connector. Some manufacturers also provide dedicated parallel
port to USB adapters designed specifically for their own DSO fitted with parallel
ports. If in doubt it is wise to contact the supplier for their advice concerning
connection to a PC.
The DSO software is usually supplied on CD-ROM (or can be downloaded
from the manufacturer's web site). It is important to note that although the
DSO hardware cannot usually be used without the appropriate software some
manufacturers supply software drivers that will allow you to control the DSO
and capture data into your own applications. However, for most of us this is not
an option since the supplied software will usually outperform anything that we
can write ourselves!
A DSO combines elements of both hardware and software. These must work
together to provide all the functionality of a conventional DSO but also those
