Teledyne LeCroy AORM - Advanced Optical Recording Measurements - Manual (Page 24)

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ISSUED: June 2013 923133 Rev A
Trend Calculation
Once the trend has been configured, parameter values will be calculated and trended on each
subsequent acquisition. Immediately following an acquisition, its trend values will be calculated.
The resulting trend is a waveform of data points that can be used the same way as any other
waveform. Parameters can be calculated on it, and it can be zoomed, serve as the x or y trace in
an XY plot, and can be used in cursor measurements.
The sequence for acquiring trend data is:
1. trigger
2. waveform acquisition
3. parameter calculations
4. trend update
5. trigger rearm
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 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 parameter buffer allows you to include up to one million values in the trend calculation.
Parameter Events Capture
The number of events captured per waveform acquisition or display sweep depends on the
parameter type. Acquisitions are initiated by the occurrence of a trigger event. Sweeps are
equivalent to the waveform captured and displayed on an input channel (1, 2, 3, or 4). For non-
segmented waveforms, an acquisition is identical to a sweep. Whereas 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 trend events.
Reading Trends
A trend is like any other waveform: its horizontal axis is in units of events, with earlier events in
the leftmost part of the waveform and later events to the right. And its vertical axis is in the same
units as the trended parameter. When the trend is displayed, trace labels appear in their
customary place on the screen identifying the trace, the math function performed, and giving
horizontal and vertical information:
• # number of events per horizontal division
• Units per vertical division, in units of the parameter being measured