One of the questions we get asked
often is about order of EMI/EMC testing. Neither MIL-STD-461 nor
RTCA/DO-160 specify the order of test performance. Leaving aside the
issue of Safety of Flight tests for aircraft (which typically must be performed
prior to any other testing), there are a few different approaches to take in
this regard.
The first approach is to begin
with the most benign tests, usually the emissions. These tests have
virtually no chance of harming the equipment under test (EUT), while conversely
they sometimes prove to be the most problematic. Emissions problems can
be notoriously difficult to track down and eliminate, and sometimes solutions
to bring them within specification requirements involve redesigns that can have
potential effects to other tests. If the other tests have been performed
prior to the emissions testing, then any changes made to bring the emissions
into spec would need to be evaluated to determine if the other tests need to be
repeated.
The second approach is to begin
with the most potentially damaging tests first. The philosophy here is
that all is well and good if the EUT endures those tests with no issues.
However, if there are susceptibilities that require repair/redesign,
those problems can be resolved before continuing with the other tests.
The third (and in my opinion
best) approach is to perform an analysis of the EUT before going to the lab, to
determine what tests are most likely to cause problems, and to start with
them. Similar to the other two approaches, the idea is that any problems
resulting from these tests can be identified and fixed before moving on to
other testing. The main difference between this approach and the other
two approaches is that because of the analysis performed beforehand, there is
some degree of confidence that the subsequent tests will be successful. See more...!
