![LeCroy DDA-3000A Скачать руководство пользователя страница 417](http://html1.mh-extra.com/html/lecroy/dda-3000a/dda-3000a_operators-manual_1866311417.webp)
X-Stream Operator’s Manual
WM-OM-E Rev I
415
Parameter
Settings
When you select
nlts
from the
PRML
dialog's
With parameter
field (
D
RIVE
A
NALYSIS
Æ
Measure
Æ
Parameter Set
Æ
PRML
) an nlts
Pattern Length
field
and pattern
Delay
field appear also. You can adjust the mantissa, exponent or
number of mantissa digits using the pop-up numeric keypad. The pattern length
should be set to the pattern period.
Although the DDA searches for the correct pattern length, the value provided
needs to be sufficiently close to the actual pattern length for
nlts
to perform the
search. A 1 µs pattern may, for example, accept a range of 1 µs +/- 40 ns. Within
this range, a value for
nlts
will be provided. Otherwise "---" appears on the screen,
indicating that no measurement can be made.
The pattern
Delay
setting is a percentage of the pattern length. The DDA will
internally scale the delay value entered by the ratio of the pattern length calculated
internally to the pattern entered by you. Several disk drive waveform attributes can
be measured by using different delay values. The following table provides delay
values to enter for the commonly used 127-bit pseudo-random sequence (x
7
+ x
3
+ 1 polynomial) when measuring various waveform attributes:
Waveform Attribute
Bit Cell
Location
Delay (%)
Adjacent Location
25.5
20.08%
2nd Adjacent Location
-30.5
-24.02%
Initial Magnetization
45.5
35.83%
Interaction Interference
-60.5
-47.64%
Notes
The pattern
Delay
tells the DDA where in the repeating pattern to measure NLTS.
NLTS is calculated from the correlation coefficient at that time. Correlation is
calculated at 3 sample times: the nearest sample time and one on each side. A
curve fit is performed to calculate a better estimate of the true peak height.
As described above, the
nlts
parameter only requires one waveform. Each
acquisition must contain only the pseudorandom repeating sequence (PRS), not a
servo wedge or a preamble. It does not matter where in the PRS the acquisition
begins; its echo properties are independent of starting point. There must be at
least two repetitions of the pattern in each acquisition. A reasonable number
would be about 25 repetitions (32 repetitions of a 127-bit sequence should fit in a
sector).
NLTS requires at least 5 samples per PW50 for acceptable accuracy. More is
better.
Содержание DDA-3000A
Страница 1: ...LECROY X STREAM OSCILLOSCOPES O P E R AT O R S M A N U A L SEPTEMBER 2006 ...
Страница 18: ...16 WM OM E Rev I BLANK PAGE ...
Страница 64: ...62 WM OM E Rev I icon in Channels dialog zooms one trace zooms all displayed traces ...
Страница 65: ...X Stream Operator s Manual WM OM E Rev I 63 then Math Setup then Measure Setup then Utilities Setup ...
Страница 80: ...78 WM OM E Rev I 4 Select a language 5 Click Next when the Wizard appears ...
Страница 81: ...X Stream Operator s Manual WM OM E Rev I 79 6 Select Complete setup ...
Страница 157: ...X Stream Operator s Manual WM OM E Rev I 155 ...
Страница 170: ...168 WM OM E Rev I 5 Read the status information in line StatusDescription ...
Страница 214: ...212 WM OM E Rev I Delay Parameter Find Range selected ...
Страница 263: ...X Stream Operator s Manual WM OM E Rev I 261 ...
Страница 284: ...282 WM OM E Rev I ...
Страница 285: ...X Stream Operator s Manual WM OM E Rev I 283 Using a Surface Plot Excel Example 5 ...
Страница 321: ...X Stream Operator s Manual WM OM E Rev I 319 Further Examples of MATLAB Waveform Functions Negate the input signal ...
Страница 324: ...322 WM OM E Rev I ...