deperm

To degauss or demagnetize; especially, to degauss a ship by dragging a large powered electrical cable along its side.

Vessels wiped and depermed as outlined above were found to age towards their original state, so the processes as described were only effective for comparatively short periods and had to be repeated at regular intervals.

Our present system deperms more reliably and is arranged to deperm the sensor each time the power source for the magnetometer is turned on.

The act or process of deperming.

Fortunately a very pronounced extension of life was found to be possible for wipes and deperms by making the initial current very strong so that, for example, a positive component was made a larger negative one before being reduced to zero […]

One interesting feature of the S/N 008A and S/N 009 data is that the residual moment after deperms one through three increased from 735 to 870 pole-cm for S/N 008A, but decreased from 854 to 659 pole-cm for S/N 009.