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Magnetic Shielding Enclosure for Computer VDUs - Specifications

Cathode ray tube (CRT) based computer display units can be subjected to low frequency magnetic field interference in their operating environments. Such interference is evident by jittering, wavering or rapid vibration of the screen picture. Prolonged used of such displays cause eyes strain, headaches and reduces the operator productivity.

A simple and most effective way of eliminating the interference is to use our very effective "Magshield" - the VDU shielding enclosure. It eliminates or substantially reduces VDU interference caused by DC or low frequency AC (50-60Hz) magnetic fields. Magshield is ergonomically designed to blend in with computer hardware and is build to suite the customer dimensions.

There is also an additional benefit from using our Magshield enclosure. It reduces low frequency radiation emitted by many common type VDUs, by up to 50%, thus bringing them in line with the Swedish Guidelines for visual display units. The latest Swedish Guideline, commonly referred to as the MPR-III, recommends that the magnetic field emitted by CRT based VDUs in the frequency range of 5Hz-2kHz should not be greater than 2.0 milliGauss at 30 cm distance from the screen. Our enclosures can satisfy this requirement even when used with the most 'offensive' VDUs.

The following is brief technical information on our Magshield VDU enclosures:

  • The shielding material used in the enclosure has high permeability value. The metal core of the enclosure is sandwiched between two layers of plastic material, which form the ergonomic outer shell of the Magshield. The amount of shielding material used in the enclosure depends on the level of external electromagnetic field.
  • The Magshield enclosure is a four-sided hollow box. It is made of a non-see through, milky-white Acrylonitrile Butadiene Styrene (ABS) plastic. ABS was chosen because of the balance between its mechanical properties (e.g. impact, tensile and flexural strength) and its heat stability and chemical resistance. Its colour blends well with off-white cases of many commercial CRT based monitors.
  • The maximum wall thickness of the Magshield enclosure is 9.0mm. The enclosures can be custom built to suit any computer monitor dimensions. There are, however, standard sizes to suit most common types of monitors on the market. For example, a Magshield enclosure with the following internal dimensions is suitable for the majority of 14" and some 15" VDU monitors:

    Width (W) = 380mm
    Height (H) = 400mm
    Depth (D) = 410mm
  • The Magshield enclosure is supplied as one integral piece. It requires no assembly.
  • The Magshield enclosure is designed with provision for adequate air circulation to prevent any adverse effect on the VDU heat dissipation. For this reason it has no back wall.
  • Shielding effectiveness of the Magshield enclosure is directly proportional to the amount of the shielding material used. The standard design Magshield enclosure is effective for shielding DC or low frequency AC (50Hz or 60Hz) magnetic fields density of up to 0.2 Gauss. This is more than adequate for the majority of VDU operating environments encountered.

    It should be noted that the Magshield enclosure is most effective when the interfering magnetic field is induced in the orthogonal direction to the screen (Bz and Bx in the sketch below). Such condition can be easily met by reorienting the VDU on the desk or in the office.

    The shielding enclosure is most effective against magnetic fields in Z and X directions. Turn the VDU by 90 degrees around its Z-axis if the magnetic field is predominantly in the Y direction.

  • Weight of the average 14" or 15" VDU enclosure is less than 7 kg.
  • For better shielding effectiveness the monitor should be inserted inside the Magshield enclosure such that its screen face is at least 40 mm inside the front edge of the enclosure.
  • The prices of the magnetic shield enclosures are as follows:
    • Average 9" CRT based monitor - AU$335.00
    • Average 14" CRT based monitor - AU$385.00
    • Average 15" CRT based monitor - AU$385.00
    • Average 17" CRT based monitor - AU$460.00
    • Average 20" CRT based monitor - AU$550.00
    • Please ask for a quantity discount and "non standard size" pricing.

    The above prices are excluding sales tax, delivery and insurance. Airfreight prices for overseas deliveries are relatively inexpensive and often cheaper than shipping by sea. Please provide us with the name of your preferred shipping company. To enquire on this product or other products, see our contact information.

    There is a large variety of CRT based monitors on the market. Each make and model has its own external dimensions. It is the responsibility of our customers to accurately specify the external dimensions of the monitors for which the shielding enclosures are being ordered. Each shielding enclosure is packed and delivered in a separate carton box.