An
automatic test is a set of X-Y plots and frequency scans that are executed
sequentially. An automatic test is used to compare a sample PCB against a
reference board. To set up an automatic test it is first necessary to
produce the X-Y plots and frequency scans that categorise the PCB. These
will be produced from the reference board. Typically an auto test will be
made up of a frequency scan of all the cables attached to the PCB plus X-Y
plots at the worst frequencies. For each test, tolerances can be set for
the levels by which the sample board can exceed the emissions of the
reference. When each plot/scan is complete the sample results are
compared to the reference and if the difference in emission levels exceeds the
specified tolerance the sample fails the test.
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