High level shielding effectiveness against EMI/RFI with high optical transmissivity
Some
electronic
equipment operation can be temporarily impaired
or it may become irrevocably damaged by exposure
to radiated electrical energy in the form of EMI/RFI.
Often times it is the most sensitive, most
expensive and critical equipment which may
experience this type of degradation. In these
cases, the EMI/RFI signals may gain access to the
sensitive electronics circuitry inside the
equipment through various indicative type performance or viewing devices,
that are necessary for human
interaction/interpretation such as
digital read-outs or displays (including touch-screens).
These read-outs and displays are designed
specifically for high visual optical transmissivity,
but generally also exhibit low shielding
effectiveness against EMI/RFI.
Shielding Express
Inc. has
developed a complete product line of shielded optical windows
that are designed to provide high visual optical transmissivity while preventing the
transmission of deleterious EMI/RFI. These windows can be
installed so as to become an integral part of an
equipment display.
Shielded windows are available with both woven
conductive metal screen laminated between polycarbonate or glass
and knitted wire-mesh
homogeneously imbedded in a clear or colored acrylic substrate. These unique
windows are designed to allow up to 95% clarity in viewing characters or
displays while, at the same time, introducing a high degree of shielding, thus
preventing equipment damage due to incident radiated electrical
energy.
Key Features
-
Windows are
constructed using a full-lamination process that results in the
conductive wire mesh being
completely encased. This permits operation under severe environmental
conditions.
-
Different wire mesh
patterns and metal alloys allow for a selection of performance characteristics
most suitable to the customer's needs.
-
The molded plastic
window substrate can be supplied in several preferred colors for improved
viewing.
-
Windows may be mounted
directly to the equipment interface via a conductive gasket and fasteners, or
mounted within a metallic bezel.
Typical Shielding Effectiveness (dB):
7" X 9" Test Window with Woven Screen Mesh
SS/Ag Blackened 0.0012" dia. wire |
200MHz |
400MHz |
800Mhz |
1000 MHz |
50 opi |
49 |
50 |
50 |
50 |
80 opi |
62 |
59 |
57 |
56 |
100 opi |
|
64 |
63 |
62 |
Note: Shielding
effectiveness will vary depending upon
the selection of wire diameter, metal alloy, and
screen openings per inch (OPI). The values
of shielding effectiveness for the windows listed
in the table above are typical. The results
were obtained from tests conducted at Shielding
Express Inc. utilizing a modified version of
MIL-STD-285. Test windows were nominally 7" X
9"
A wide variety of shielding materials and window
features are available (see information
below) to meet the requirements of your
application.
Materials and Features: |
|
Thickness of
Window: |
.062"
to .250" |
|
Knitted
Wire Screen: |
0.0012
- 0.0022 dia. wire, 50 - 145 OPI (Std) Woven Copper or Stainless Steel,
Blackened. |
|
Color: |
Clear
(STD) or contrast enhancement |
|
Optical
Finish: |
Anti-reflection coatings; Non-glare, various gloss levels
available; Chemical and scratch resistant |
|
Terminations: |
Silver
filled bus; Extended wire mesh; Compression gaskets |
|
Environmental: |
MIL-STD-202A Thermal, Vibration, Moisture, and Temperature
Cycling. |
|
Optical
Medium: |
Cast
Acrylic per Federal Specification L-P-391, Type 1, Grade C (Std) Glass and
Polarizers (Optional). |
|
Typical Edge
Termination:
|
Available materials;
glass, ploycarbonate, acrylic, and polarizer. |