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Head TEST method Disclosure Number: IPCOM000015777D
Original Publication Date: 2002-Mar-30
Included in the Prior Art Database: 2003-Jun-21
Document File: 3 page(s) / 76K

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Head TEST method


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Disclosed is the method to test GMR head in terms of instability and center shift. Test algorithm is described below. By using this algorithm, both amplitude instability and center shift could be expressed as numeric number so that bad head could be rejected by simply setting criteria. Write an amplitude burst pattern at the center of the track.(A in fig1),write second pattern at little off track position(B in fig1), write third pattern at opposite off track position(C in fig1) Read these three pattern while read head is on the center of the track, read back amplitude from them are expressed as

       ((((((((((((Va x Vb Vc((( where Va is readback amplitude of pattern A,Vb is readback amplitude of pattern B,Vc is readback amplitude of pattern C. k is also expressed as

       k(k(((([Wr Xoff Ww-Wr)] Wr(((k where Wr is the read head width, Ww is the write head width, and Xoff is off track position where pattern B and C were written..

Since write head width and read head width are constant value for each, K is dominant by Xoff. Test sequence is 1. Keep read head stay at the center of the track, just read A,B,C pattern.

2 At the same position read A,B,C pattern while writing pattern other than the time when A,B,C

is reading. (If it is needed write current or read bais should be changed)

Assuming Va1,Vb1,Vc1are the each burst amplitude while not writing, and Va2,Vb2,Vc2 are the

amplitude while wri...