LeCroy DDA 7 Zi series, Operator'S Manual

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WavePro 7Zi
389
WP700Zi-OM-E-RevA
4. You can touch the Find Center and Height button to automatically locate the center of the Trend
waveform and to scale it to fit within the grid, without affecting zoom and position settings. Or you can enter
specific values by touching inside the
Center and Height data entry fields and typing in values, using the
pop-up numeric keypad.
5. You can also touch the Enable Auto Find checkbox if you want the instrument to
continuously self-adjust Center and Height.
Histogram and Trend Calculation
With the instrument configured for Histograms or Trends, the timing parameter values are calculated and the
chosen function performed on each following acquisition. The Histogram or Trend values themselves are
calculated immediately after each acquisition.
The result is a waveform of data points that can be used the same way as any other waveform. Other parameters
can be calculated on it, it can be zoomed, serve as the
x or y trace in an XY plot, or used in cursor
measurements.
Acquisition Sequence
The sequence of events for acquiring Histogram or Trend data is:
1.
Trigger
2.
Waveform Acquisition
3.
Parameter Calculations
4.
Histogram Update
5.
Trigger Re-arm
If the timebase is set in non-segmented mode, a single acquisition occurs prior to parameter calculations.
However, in segment mode an acquisition for each segment occurs prior to parameter calculations. If the source
of the Histogram or Trend data is a memory, storing new data to memory effectively acts as a trigger and
acquisition. Because updating the screen can take significant processing time, it occurs only once a second,
minimizing trigger dead-time. (Under remote control, the display can be turned off to maximize measurement
speed.)
Parameter Buffer
The instrument maintains a circular parameter buffer of the last 20,000 measurements, including values that fall
outside the set histogram range. If the maximum number of events to be used in a histogram or trend is a number
N less than 20,000, the histogram will be continuously updated with the last N events as new acquisitions occur. If
the maximum number is greater than 20,000, the histogram or trend will be updated until the number of events
equals
N . Then, if the number of bins or the histogram or trend range is modified, the instrument will use the
parameter buffer values to redraw the histogram with either the last N or 20,000 values acquired, whichever is the
lesser. The parameter buffer thereby allows histograms or trends to be redisplayed using an acquired set of
values and settings that produce a distribution shape with the most useful information.
In many cases the optimal range is not readily apparent, so the instrument has a powerful range finding function.
If required, it will examine the values in the parameter buffer to calculate an optimal range and redisplay the
histogram or trend using it. The instrument will also give a running count of the number of parameter values that
fall within, below, and above the range. If any fall below or above the range, the range finder can then recalculate
using these parameter values, while they are still within the buffer.
Parameter Events Capture
The number of events captured per waveform acquisition or display sweep depends on the type of parameter.
Acquisitions are initiated by the occurrence of a trigger event. Sweeps are equivalent to the waveform captured
and displayed on an input channel.
For non-segmented waveforms, an acquisition is identical to a sweep, but for segmented waveforms an
acquisition occurs for each segment and a sweep is equivalent to acquisitions for all segments. Only the section
of a waveform between the parameter cursors is used in the calculation of parameter values and corresponding
histogram events.