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The most critical task an electronics test engineer can
face is evaluating platforms for their test system.
The same test system is often used throughout the
development cycle, from design and prototyping to validation and
manufacturing.
Therefore, the choice of
your test system can affect your entire product development
process. A crucial
factor when choosing your test system is matching your test
instruments to the specifications and requirements of your Unit
Under Test (UUT). These
UUTs can range from cell phone components to automotive ECUs.
Using the same system throughout the design cycle or for
several different UUTs, requires that the platform be extremely
flexible. Overall
system cost is also imperative when assembling your test system.
These requirements are some of the most critical that are
considered when evaluating test platforms.
If the primary concerns are identified early in the system
evaluation, engineers could save time, money, and headaches during
the entire development process. For small to medium size test
systems, engineers can assemble an entire test system on one
platform. Larger test
systems frequently require hardware from several platforms to meet
specifications. For
example, a PXI (PCI eXtensions for Instrumentation) based test
system offers the flexibility to expand your system to stand alone
and VXI instruments and the software to tie it all together.
Meeting
the necessary measurement requirements for a UUT is often a major
challenge when assembling your test system.
A measurement device has to match certain requirements to
validate a given specification.
For example, a device in manufacturing test applications
must meet a minimum Test Accuracy Ratio (TAR).
TAR, a metric that gauges the uncertainty of an overall
measurement, should be at least 4 to 1 for most manufacturing test
applications. Frequency
is also a common requirement to be met by the measurement device
in order to capture the entire response waveform.
The Nyquist theorem states that a signal must be sampled at
a rate greater than twice the highest frequency component of the
signal to accurately reconstruct the waveform; otherwise, the
high-frequency content will alias at a frequency inside the
spectrum of interest (passband). An alias is a false lower
frequency component that appears in sampled data acquired at too
low a sampling rate. In
order to properly capture the entire waveform shape the signal
should be sampled at eight to ten times its own frequency.
Another specification that is often crucial when evaluating
test platforms is the total number of Input/Output (I/O) channels.
These channels will need switches, fixtures, and in some
cases high channel ...
...Continued
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