Shielded Vent Panels

> General design and use guidance

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	A selection of standard vent panel sizes (Metric)
	A selection of standard vent panel sizes (Imperial)

Honeycomb vent panels

The most commonly used type of vent is based on aluminium honeycomb panels mounted in an extruded aluminium frame. The honeycomb media has a very high open area and therefore allows good air flow with minimal pressure drop. In order to achieve the best shielding performance two layers of honeycomb are used orientated at 90° to one another, although this is not always necessary on some less demanding applications. The exterior facing honeycomb layer can be angled (usually 45°) so as to direct airflow in a particular direction or to deflect rain or spray. Whilst this can be a useful feature to include in a vent design it should be borne in mind that it will impede airflow, particularly at higher air speeds.

Other types/shielding media

Vents may also based on other media types such as woven or expanded mesh to make very low profile units or combined filter vents.

High performance vents

There are also some types of vent designed for very high levels of performance and / or more arduous conditions. There are two methods of construction that can be used if this is the case.

Machined from solid -
The vent can be machined from a solid aluminium billet or plate. The open area of the vent is created by a drilled matrix of holes that utilises the waveguide beyond cut-off effect of holes that have a diameter approximately one quarter or less of there length.

Fully brazed/solder steel construction -
Alternatively these types of vents may be fabricated from interlocking steel strips that are then fully brazed and then over plated with zinc or tin. This type of construction provides outstanding shielding performance particularly in the ‘H’ field or magnetic region

Low Cost Vent Panels

We stock a range of low cost plastic (Aluminium honeycomb) EMC vents for use with 40mm, 60mm, 80mm, 92mm & 120mm fans. They provide EMC shielding where applications demand a low cost solution, whilst still providing an adequate shielding performance.

A Hi-impact ABS UL94V-0 fire retardant moulding is fitted with one layer of 3.2mm cell x 6.35mm thick honeycomb and a nickel over copper plated fabric over foam gasket to ground the honeycomb to the metalwork. The vents have 4 countersunk holes to suit standard fan mountings.

Shielding Effectiveness Measured performance in accordance with MIL-STD 285 (80mm tested) Frequency Field Typical (db) 200kHz H 53 100Mhz E 102 500MHz P 85 2GHz P 74 10GHz P 58

These are available 'off the shelf' for fast delivery and significantly more cost effective if small volume shielding vents are required.

Applications

Honeycomb vent panels are used wherever there is a requirement for a high level of air flow and shielding performance such as

Heating ventilation and air conditioning systems
Cooling high power systems/circuits e.g. radar, RF comms, power supplies, etc
Generators
Welding unit
Engines