tokens: The test sequence shall be as follows : 1 . EUT not operating , initial measurements on the six semi - axes at the reference distances . 2 . Deperm : ( a ) EUT not operating , application of a deperming field in accordance with Figure 5 - 12 frequency 3 Hz , maximum amplitude between 4 000 µT and 5 000 µT , successively on each XYZ axis of the EUT . NOTE 1 This is usually done using Helmholtz coils . NOTE 2 A sequence of symmetrical sine periods of increasing and decreasing amplitude gives better results than a sine wave modulated by exponentials or ramp functions . ( b ) Measurement after deperm on the six semi - axes at the reference distances . 3 . Perm : ( a ) EUT not operating , application of a perm field of 300 µT on each XYZ axis . ( b ) Measurement after perm on the six semi - axes at the reference distances . 4 . Stray field : EUT operating , measurement on the six semi - axes at the reference distances . 5 . Final deperm : repeat 5.4.5.3a.2 .