57O48-1414-3600 Spectrum Control, 57O48-1414-3600 Datasheet - Page 4

• Manufacturer Part Number: 57O48-1414-3600
• Description: EMI SHIELDING GASKET, ROUND
• Manufacturer: Spectrum Control

Specifications of 57O48-1414-3600

• Body Material: Wire Mesh Over Conductive Elastomer Core
• Attenuation: 100dB
• Length: 36"
• Gasket Style: Round
• Thickness: 0.14"
• Diameter: 0.14"
• Height: 0.14"
• Leaded Process Compatible: Yes
• Gasket Material: Metal Mesh
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4
Shielding Theory and Introduction
Shielding Theory
Electromagnetic shielding is used to prevent electromagnetic
signals such as radio signals from leaving or entering a box
or enclosure. Signals inadvertently emitted by an electronic
device can cause distortion or interruption in normal radio
communications in a localized area. This is the basis of
most laws and regulations concerning electromagnetic
interference. In addition, normal radio signals can cause
unprotected electronic devices to malfunction. Depending
on the device’s function, a malfunction in the device could
be a minor inconvenience such as static on a radio, or life
threatening such as the malfunction of a life support system
at a hospital.
Introduction
The electromagnetic shield in most cases is the electronic
housing itself. The housing/shield forms a metal cage around
the electronic circuits in a device. Most of the electromagnetic
signal is absorbed with a small portion (3 to 10 dB) of the
signal reflected off the metal housing. Most of the absorbed
signal creates alternating currents at radio frequencies which
travels on the surface of metal. This allows the
electromagnetic shield to keep signals from outside the
enclosure on the outside of the shield and signals from
inside signals on the inside of the shield.
SPECTRUM CONTROL INC. • 8031 Avonia Rd. • Fairview, PA 16415 • Phone: [phone] • Fax: [phone] • Web site: www.specemc.com
SPECTRUM CONTROL GmbH • Hansastrasse 6 • 91126 Schwabach, Germany • Phone: [phone] • Fax: [phone]
100.
.001
10.
.01
1.
.1
100 KHz
60 dB
80 dB
1 MHz
40 dB
SHIELDING EFFECTIVENESS
20 dB
10MHz
Frequency (MHz)
100MHz
1GHz
Wavelength
Frequency
10GHz
to
100GHz
no holes in the electromagnetic shield which would allow
the currents to flow from one side of the shield to the other.
Holes are a necessity in an electronic enclosure. Connectors,
wires, and cables are needed to transmit information to and
from electronic devices. Doors and covers are needed to
get access to components to maintenance, service, and
keypads may also be required. The problem is that all of
these items cause openings in the shield which reduce
the performance of the shield.
ventilation panels, shielded filtered connectors, and shielded
switches minimize the effect of a hole in the shield.
that needs to be shielded are the major factors determining
the shielding effectiveness of an electronic enclosure. The
distance between spotwelds, or screws which hold a metal
housing together count as long narrow holes. Higher frequencies
(lower wavelengths) flow more easily through smaller holes,
and so the highest frequency needed to be shielded is the
frequency of concern when designing shielding.
estimate of the shielding effectiveness of a metallic
electronic housing.
110
100
90
80
70
60
50
40
30
20
10
The shield will continue to function as long as there are
Special devices such as shielding gaskets, shielding
The length of the hole and wavelength of the signal
Aperture versus frequency charts can give a rough
0
0
100
Test Fixture: Flanged coaxial transmission line
TYPICAL SHIELDING EFFECTIVENESS
200
Test Methods: ASTM D-4935-89
300
Frequency (MHz)
400
500
600
700
800
900
1000