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Measurement Definition
Measurement Parameter Definition
•
Ts denotes the time distance from negative peak transition to positive peak transition
(n-p).
•
N denotes the number of transitions to be averaged.
Time Asymmetry is also used in measuring the hard transition shift (HTS) based on the
timing difference between the positive and negative peaks of the low frequency signal
written on the magnetic medium after the medium was DC erased.
Narrow Band TAA Measurement
Narrow band TAA is defined as the average amplitude for several revolutions. Because it is
measured by a spectrum analyzer, you can measure small amplitude signals due to the
spectrum analyzer's sensitivity. Unlike the TAA measurement, where parametric module
and oscilloscope are used.
The Agilent E5022/E5023 measures the peak voltage at the fundamental frequency of the
data pattern. For example: if the HF data pattern is selected, the repetitive period is set at
2T and the channel bit rate is set at 100 Mbps. When the frequency mode is auto in the
"hpe5022_narrowBandTaaFreqMode" function, the center frequency of the spectrum
analyzer is set at 25 MHz and the spectrum analyzer measures the amplitude at this
frequency.
Stability Measurement
Stability measurement is used to observe the amplitude variation of signals during the
write-read iterations of the head in individual sectors (segments) on a track. A write data
pattern is written for one revolution. After that the previously written track is divided into
segments by controlling the write operation and read operations. In order to divide the
track into segments as shown in Figure 5-8. The previously written data pattern is
overwritten for a short time which is called write excitation. This is followed by a delay
time before the previously written data is read.
E5022/E5023 allows the user to achieve a higher throughput when track is divided into
sectors. For example, if the user decides to measure the TAA for ten loops, you can reduce
this to five provided that the track is divided into two sectors. By shortening the time to
measure it allows the test have a higher throughput.
The measurement sequence is as follows:
1. Write a data pattern on the track for one revolution.
2. Read the written data from the specified segment (sector) as defined by the write and
read ratio.
3. Calculate the TAA or PW of the read data.
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Chapter 5
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