Teledyne LeCroy WaveExpert 100H Operators Manual - Manual (Page 137)

Wave Expert
WE-OM-E Rev A
135
Histogram Peaks
Because the shape of histogram distributions is particularly interesting, additional parameter
measurements are available for analyzing these distributions. They are generally centered around
one of several peak value bins, known, with its associated bins, as a histogram peak.
Example: In the following figure, a histogram of the voltage value of a five-volt amplitude square
wave is centered around two peak value bins: 0 V and 5 V. The adjacent bins signify variation due
to noise. The graph of the centered bins shows both as peaks.
Determining such peaks is very useful because they indicate dominant values of a signal.
However, signal noise and the use of a high number of bins relative to the number of parameter
values acquired, can give a jagged and spiky histogram, making meaningful peaks hard to
distinguish. The scope analyzes histogram data to identify peaks from background noise and
histogram definition artifacts such as small gaps, which are due to very narrow bins.
Binning and Measurement Accuracy
Histogram bins represent a sub-range of waveform parameter values, or events. The events
represented by a bin may have a value anywhere within its sub-range. However, parameter
measurements of the histogram itself, such as average, assume that all events in a bin have a
single value. The scope uses the center value of each bin's sub-range in all its calculations. The
greater the number of bins used to subdivide a histogram's range, the less the potential deviation
between actual event values and those values assumed in histogram parameter calculations.
Nevertheless, using more bins may require that you perform a greater number of waveform
parameter measurements, in order to populate the bins sufficiently for the identification of a
characteristic histogram distribution.
In addition, very fine grained binning will result in gaps between populated bins that may make it
difficult to determine peaks.
The oscilloscope's 20,000-parameter buffer is very effective for determining the optimal number of
bins to be used. An optimal bin number is one where the change in parameter values is insignificant,