LeCroy DDA 7 Zi series, Operator'S Manual

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WavePro 7Zi
379
WP700Zi-OM-E-RevA
When you need to
Use…
monitor the evolution of a waveform
parameter
or attribute over several acquisitions...
Trend — Jitter works only on one acquisition at a time
time-correlate an event and a parameter
value...
JitterTrack
monitor an evolution in the frequency
domain...
JitterTrack — Trend points are not evenly
spaced in time and therefore cannot be used for FFT (Fast Fourier
Transform).
monitor JTA parameters...
Trend
Figure 5-27. Random NRZ (Non-Return to Zero) data stream and its corresponding clock signal.
Clock or Data?
For most waveform attributes, JitterTrack offers the choice of Clock or Data modes for measuring clock signals or
data streams. "Data" should be used (where available) when the pulse widths, intervals, periods or other
significant instants being measured are randomly distributed and contain multiples of the clock period.
On the one hand, apart from jitter, clock signals ought to be regular. On the other hand, data streams by their very
nature have irregular pulse widths.
A clock signal is normally required to characterize jitter. But such a signal will not be available if the waveform
being measured is a data stream, whose very randomness hides the clock signal. To overcome this, JitterTrack
provides both Clock
and Data modes. Selecting Data from the VClock
dialog gives the superior timing resolution through
normalization (see table ) required for correctly measuring jitter in data signals.