3M CTK015, Руководство пользователя

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a far-field test, the field strength greatly depends on the antenna properties
of the radiating object. As an example, a short trace on a PCB with a strong
emission level may be much less dangerous than a longer one with a lower
emission level. A strong but small emission leak from an otherwise shielded
enclosure may be much less of a problem than “lukewarm” radiation from a
large area or around a long seam in the shield. If the offending frequency is
well-known and if the field carrying it is not the strongest one in the product,
a spectrum analyzer may be a more appropriate tool. If the probe is used in
the early stages of development where it is not yet clear what frequency will
be of concern, the 3M
™
ScanEM-C Electromagnetic Near-Field Probe will
prove to be quick and effective. In some cases the ScanEM-C Probe’s own
indication may actually do a better job than a spectrum analyzer in searching
for the highest emission levels, since the spectrum analyzer won’t provide
a total signal level. It is difficult to subjectively judge it by looking at the
screen.
Troubleshooting
Common Places to Look for Excessive Emissions
Each product is unique. However, there are common areas to watch for in
almost any product. Such places include:
Inside the box:
‰ Long traces carrying digital signals
‰
Microprocessors
‰ Memory chips (including cache memory)
‰ Disk controllers
‰ Buffers
‰ Any cable or cable assembly within the product