Tektronix TDSDDM1, User Manual, Page: 61 / 102

Measurement Descriptions
TDSDDM1 Disk Drive Measurement Application User Manual
3–19
4. Wait for the measurement to complete, then view the results as shown in
Figure 3–12.
The application performs the measurement according to the following algorithm:
1. Set the disk drive to the specified speed.
2. Position the head to the desired gap, radius, and skew angle.
3. Precondition the media service. (See the IDEMA standard, document T3-91,
for information about preconditioning the media service.)
4. Write the specified frequency at the specified current for one revolution of
the disk.
5. Measure the peak-to-peak analog amplitude of the Read signal for one entire
revolution, excluding all non-uniform segments, such as write splices, servo
gaps, and header fields.
The hysteresis setting is used when looking for peaks.
6. Compute the track average amplitude around the entire track by summing up
the peak-to-peak voltages of each plus and minus pulse pair. Divide the
result by the number of pulse pairs.
7. Perform the measurement by acquiring one segment at a time, measuring it,
and combining all the results for the final value. To speed up the measure-
ment process the user can specify a smaller region of each track segment to
measure by using the cursors or by decreasing the record length.
This measurement requires the user to specify the number of segments on the
track to be tested.
8. Use a value of 1/2 of the TAA value as the threshold level at which to
measure the pulse width of each positive and negative pulse. Compute the
average pulse width around the track for all pulses measured.
9. Display the measurement result. (The display also reads out the standard
deviation of the measurement for all pairs used.)
The pulse width at 50% measurement, PW50, is the average width of a group of
positive and negative pulses. The pulses making up the tested group are selected
by the following criteria:
H
There must be enough pulses around the recording track to provide an
adequate statistical sample.
H
The spacing between pulses must minimize any interaction between the
measured pulses.
Test Methodology