IP 55 Modular Cabinets

ELECTROMAGNETIC COMPLIANCE
TEST PERFORMANCE
Attenuation (dB)
Attenuation (dB)
BOARD ATTENUATION H=2000 L=800 P=600
Cabinet equipped with EMC clips
Cabinet with zinc-coated internal
faces and sealing edge, matched
with shielded rubber gaskets.
Standard cabinet
Frequence (MHz)
BOX ATTENUATION L=400 H=500 P=200
Frequence (MHz)
Box with zinc-coated internal faces
and sealing edge, matched with
shielded rubber gaskets.
Standard box
The shield efficiency tests on cabinets and metal boxes
have been produced in compliance with specification 65-
6 of American NSA concerning Military Standard MIL-
STD-220.
The first graph compares three different types of boards.
Standard, equipped with EMC clips and fully zinc-coated
cabinet.
It is necessary to mention that the graph can vary dramatically
according to the dimensions of the board and of
the position of the detection. In the specific case, the
detection has been performed on a spot on the back of
the board at 1400 mm from floor and centered on the
side.
The second graph compares two cassettes: the first is a
standard one and the second is fully zinc-coated
In this case it is impossible to fully comply with NSA 65-
6 standard, since the boxes are to small to maintain the
required distance (30 cm) between the transmitting
antenna and the wall of the tested box.
According to the cabinet, an anecoic chamber has been
employed.
The detection indicated has been performed on the lower
rear edges of the box.
Interpretation of the measures
To compare the noted attenuation, the following considerations
must be taken into account:
1. it is more difficult to shield a magnetic field instead of
an electric one;
2. at 50 Mhz the magetic field and the electric field
almost coincide;
3. at 50 Mhz the attenuations are lower due to a
question of impendance (the electric wave and
the magnetic wave match).
BOZZA DI STAMPA
21 CATALOGUE
176