Question
I want to do an EMI scan using a quasi-peak. Why is it recommended to first do a
pre-scan with data reduction and a peak list?
Why is it helpful to do Data Reduction?
Answer
EMI measurements may take a long time because the time constants prescribed by
the standard for quasi-peak detectors lead to long measurement times for the
whole scan. In addition, the standards stipulate procedures for finding local
EMI maxima, e.g. switching the LISN or varying the antenna and turntable.
Measuring with the quasi-peak detector at each frequency and for each test
configuration setting would lead to an unacceptably long total test time.
For this reason, it is useful to have a method that reduces the time-consuming
measurements to a minimum, with optimum reliability of detection. The best
method is to pre-analyze the spectrum in a fast prescan with a peak detector.
Data reduction follows so that the time-consuming final measurement is performed
at only relevant and selected important frequencies.
It is initiated by pressing a key after the prescan. Several data reduction methods
are possible, but it is always a peak search. The procedure selects frequencies
that have very high levels and/or that are close to your limit.
