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Measurement Definition
Parametric Sweep Measurement Definitions
Sense Current Sweep Measurement
Sense current sweep is a measurement of the TAA, narrow band TAA, PW, Overwrite and
NLTS by 5th Harmonic method. In theory the sense current head curve would be very
similar to the write current curve. In practice, the read head is heated by the DC bias and
the head will burn out due to over heating before the curve gets out of the rising region.
When doing a sense current sweep "Do not increase the current from the normal value used
for reading" unless you plan on destroying the head. A typical GMR sense current value
would be 5 [mA].
The detailed measurement sequence is described in Chapter 3 of the programming manual.
Channel Bit Rate Sweep Measurement
Channel bit rate sweep is a measurement to observe the special characteristics of TAA,
narrow band TAA, PW, Baseline, Overwrite or NLTS by 5th harmonic method with respect
to channel bit rate. In addition, it has the function to calculate bit density.
The detailed measurement sequence is described in Chapter 3 of the programming manual.
Roll-off Measurement
Roll-off is a kind of channel bit rate sweep measurement that uses 1T data pattern. It can
only measure TAA and narrow band TAA. For this measurement, flux frequency is used as
the input (sweep) parameter instead of channel bit rate.To measure "Roll-Off", the track
radius and RPM are used along with bit rate to determine the spacings between transitions.
Figure 5-44
Roll-off curve
Roll-off is the graphical plot of the voltage signal as a function of flux change density. To
plot the roll-off curve a series of 111... pattern is written throughout the track at an
Chapter 5
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