An alternating current (AC) bulk eraser (degausser) is used for complete erasure of data and other signals on magnetic media. Degaussing is a process where magnetic media is exposed to a powerful, alternating magnetic field. Degaussing removes any previously written data, leaving the media in a magnetically randomized (blank) state.

The degausser must subject the media to an alternating magnetic field of sufficient intensity to saturate the media and then by slowly withdrawing or reducing the field, the magnetic media is left in a magnetically neutral state.

To erase recorded data, it is necessary for the strength of the degaussing field to be greater in value than the coercivity of the magnetic media. Simply stated, coercivity is the magnetic field strength, rated in oersteds (Oe), required to change the magnetic orientation of the magnetic material. Check with knowledgeable dealers or degausser manufacturers to identify degausser models that meet your requirements.

Data is typically not lost until its level has been decreased 65% to 75% (or more) below its original saturation recording signal level, dependent upon the drive system.

 

For more information on cleaning up a hard drive, erasing hard drives, degaussing equipment, and degaussing services, see also: wipe it: the hard drive eraser how to delete my hard drive freeware delete all data windows me hd-1 professional hard drive eraser clean hard drive for free cannot delete data folders from outlook 2002 hd-1 eraser wipe hard drive service pf252 video tape degausser erase harddrive software v-880 degausser permanantly delete data forums v92 video tape degausser v-880 tape degausser total erase hard drive hd-1 degausser v92 video tape eraser cannot delete lexmark network port and data invalid v92 video tape degausser mds-4 audio tape eraser erase harddrive completely v-94 video tape degausser delete all data from hard disk how to delete already deleted items off your hard drive sv91m diskette degausser sv91m disk degausser pf252 video tape eraser steps for cleaning data in a data warehouse automatically erase file after reading per-4516 eraser visual basic mshflexgrid erases row data recordset hd-1 video tape degausser how can you erase data from a cd-r cds 2500a feed hopper tape eraser dlt cleaning erase hard drive computer clean hard drive free trial hd-1 degausser erase harddrive completely erase your harddrive

A complete erasure level, for most users, is considered to be 60 dB below the original signal level – this of course depends on user requirements. A 60 dB signal decrease equates to reducing the signal to one tenth of one percent of its original value.

Magnetic media products that have factory prerecorded magnetic servo patterns should not be degaussed. Degaussing would erase the factory written magnetic servo signals and leave the media unusable. For all other magnetic media (without magnetic servo signals), after proper degaussing, the quality of subsequent data recording should be unchanged or even improved.

It is very important to understand and follow the degausser’s operating instructions. This is especially important for manual units where the operator controls the media’s movement through the degaussing field. For higher coercivity media, four passes are often recommended – two passes, with a 90 degree rotation for the second pass, and then repeat the process with the media turned upside-down. Of course, these and other important operating considerations will vary with the type, power and construction of the individual degausser models.

For more information on cleaning up a hard drive, degaussers, erasing hard drives, cleaning hard drives, degaussing, and erasing harddrives, see also: