Plextor PX-712 Installation And User Manual page 86

Section 5. Advanced Features and PlexTools Professional
6. To end measurement, click the Stop button, or wait for the
measurement to stop by itself. You see a graph of the errors recorded
by the application. PlexTools Professional also tells you if the media
is safe to write at highest speed, or if you need to reduce speed to
write safely.
What the Measurements Mean
Recordable and rewritable discs can be manufactured with widely
varying quality, and a failure to write a disc without errors can be caused
by either the drive or by the media. Variations in the reflective layer,
polycarbonate thickness, eccentricity (that is, if the spindle hole is not in
the exact center of the disc), and the quality and thickness of the dye
layer are all factors that determine if the laser accurately burns the data
on to the disc.
PoweRec can reduce the drive speed during recording to ensure a higher
quality recording, but the reduction in speed may be perceived as a
problem with the drive when compared against a drive without
PoweRec.
The FE/TE graphing capability of the Plextor PX-712 drive displays the
mechanical characteristics of the disc by indicating how consistently the
laser tracks across the surface of the disc, and how accurately the focus
is maintained on the recording dye layer.
To be specific:
• Focus error is a measure of how accurately the laser is focused on
the disc surface. (That is, how round the laser dot is.) A good disc
will show a low number of focus errors across the graph. A bad disc
will show a high number of focus errors across the graph, or high
points where the drive cannot focus the laser correctly because of
poor disc quality.
• Tracking error is a measure of how accurately the laser tracks in the
disc's pre-groove area of the disc—that is, how well the laser
follows the spiral. A good disc will show low tracking error across
the graph, showing a fairly consistent track at all rotational speeds. A
bad disc will show high tracking error, which is caused by
eccentricity or poor quality of the manufactured media.
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PX-712 Installation and Users Manual