Degausser oersted strength

The Tip of the Night for April 28, 2021 discussed Degaussing, which erases magnetic storage media by altering magnetic fields. Different drives and tapes will have varying 'coercivity'. Coercivity is the intensity of the magnetic field required to eliminate the magnetization of the storage device. Different kinds of magnetic media are classified into one of three types based on their oersted count - a unit of magnetic field strength.


Type I devices will have 350 oersteds or less. Type II magnetic media have between 350 and 750 oersteds. Type III storage devices will possess more than 750 Oe.


Not all Degaussers can erase every type of magnetic media. For example, the HP LTO-8 30 TB data tape cartridge, available here, has a magnetic coercivity of 2300 Oe.

A guide to Degaussers published by the National Security Agency in June 2019, NSA/CSS Evaluated Products List for

Magnetic Degaussers, rates Degaussers based on their Oe rating. As you can see, older model Degaussers will not be able to successfully erase this HP tape.


The oersted rating for a Degausser may differ based on whether the media being erased is a drive or a tape.