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Filtering of the intake air of electronic equipment enclosures where EMI/RFI shielding is also a criteria is the task of MAJR’s line of shielded air filters. High-efficiency air filters are supplied ready to install with an EMI/RFI gasket as an integral part of the filter assembly. The rigidity of the mounting frame makes installation and removal for cleaning an easy task. The filter media used in the panels can be supplied as a dry or wet filter. Impingement of fine dust particles on filters with a glutinous oil coating is greatly enhanced.
The shielded air filter media shown represent the common sizes and mounting configurations available. In all cases, the EMI gasket is supplied as an integral part of the vent assembly.
Design Data
EMI/RFI Shielding
Shielding Effectiveness vs Frequency — Table 1
Shielding Effectiveness dB
|
Field
|
Material Code - 57
Frequency
|
|
100
kHz
|
1
MHzh |
18
MHz |
100
MHz |
400
MHz |
1
GHz |
10
GHz |
| H |
52 |
68 |
— |
— |
— |
— |
— |
| E |
— |
— |
95 |
— |
— |
— |
— |
| PW |
— |
— |
— |
90 |
70 |
65 |
50 |
|
Field
|
Material Code - 57 Trim Line
Frequency
|
|
100
kHz
|
1
MHzh |
18
MHz |
100
MHz |
400
MHz |
1
GHz |
10
GHz |
| H |
29 |
36 |
— |
— |
— |
— |
— |
| E |
— |
— |
75 |
— |
— |
— |
— |
| PW |
— |
— |
— |
60 |
60 |
60 |
50 |
The values in Table 1 show shielding characteristics for standard MAJR shielded air filters.
Note that the data indicated is based on a unit whose opening was 12.00 x 12.00 (305 x 305 mm) and tested under laboratory conditions.
Static Pressure Drop vs. Air Flow Resistance
The low resistance to air flow of these panels will minimize pressure drop within the cabinet allowing air to move freely through the intake while performing the desired dust filtration function. The curves in Figure 1 show the resistance per square inch for standard filter media.
Mounting Installation
Four mounting frames are offered as a standard for installation into the cabinet. In each case, the extruded aluminum frame is designed with a “tooth” that bites into the filter grill to ensure grounding of frame to filter media.
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