User manual

WaveSurfer 3000/3000z Oscilloscopes Operator's Manual
Calculating Measurements
The instrument uses the following methods to calculate measurements.
Determining Top and Base Lines
Proper determination of the top and base reference lines is fundamental for ensuring correct parameter
calculations. The analysis begins by computing a histogram of the waveform data over the time interval
spanned by the left and right measurement gates. For example, the histogram of a waveform transitioning
in two states will contain two peaks (see figure). The analysis will attempt to identify the two clusters that
contain the largest data density. Then the most probable state (centroids) associated with these two
clusters will be computed to determine the top and base reference levels: the top line corresponds to the
top and the base line to the bottom centroid.
Determining Rise and Fall Times
Once top and base are estimated, rise and fall times are calculated. The appropriate threshold levels are
automatically determined by the instrument, using the amplitude (ampl) parameter.
Rising Edge Duration
Falling Edge Duration
Where Mr is the number of rising edges found, Mf the number of falling edges found, the time when
rising edge i crosses the x% level, and the time when falling edge i crosses the x% level.
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