Degaussing Coils

A "degausser", is an electronic tool used for demagnetising materials, thereby eliminating any magnetic fields they may have. It usually consists of a degaussing coil, which is a copper coil with an AC current passing through it. It is an extremely useful tool for demagnetising the audio head of a cassette player, the shadow mask of a colour television screen, and bulk erasing audio and data tapes.

AC Current

An AC current from the mains usually powers a degaussing coil for a short duration before the coil heats up. An AC current produces a rapidly alternating magnetic field, which has the effect of randomising magnetic domains, thus neutralising any magnetic fields.

Applications

Modern day applications involve demagnetising data tapes, and hard drive storage devices. It is worth noting that modern hard drives use perpendicular recording methods, and those drives might not be easily demagnetised by a regular degausser. It will also not work for optical mass storage, and solid state drives.

Television Degaussing Coil

A colour television usually has a shadow mask, which is extremely sensitive to magnetism. If it becomes magnetised, it may cause improper beam landing resulting in patches of colour on various parts of the screen. If the magnetism is minor, a television receiver set may correct it automatically as many sets have a built in degaussing coil. Usually situated around the edges of the screen, and held by a rope, it automatically activates when the television switches ON. However, on some televisions, this function activates when the television goes into standby mode.

The coil usually has a temperature sensitive resistor in series, which increases its resistance as the coil heats up. Consequently, the coil remains powered for a few seconds when the television starts. This is usually sufficient for removing weak magnetic fields, however if the magnetic fields are stronger, then an external demagnetiser is required.

This Article Continues...