LeCroy WavePro 7 Zi series Operator's Manual page 473

When a waveform rises by an amount that is more than the hysteresis, compared to the lowest prior waveform
sample, the criterion for the existence of a peak is met. Then the search for its exact location and voltage value is
initiated. Successive samples are compared to find the highest sample. Next, two points are found, one on either
side of this highest sample and down from it by at least 25 % of the distance to the previous trough amplitude. A
quadratic interpolation is then performed on these three samples to find the new peak location and amplitude. The
same approach, using a sample lower than the highest sample by more than the hysteresis setting, is used to
locate the trough.
Local Baselines
Many parameter measurements require that the baseline of a local feature be identified. In order to account for
asymmetries due to MR heads, baselines are identified between the peak and trough, and between the trough
and the following peak.
The baselines are found by locating a point at which the waveform 'rests' between the peak and trough and peak.
These resting points are identified by statistically measuring the area of least change in voltage value between the
peak and trough or trough and peak, with internal tolerance levels set to ensure against false baseline
identification.
Another condition for identification is that the resting points must fall within a band, centered around the midpoint
of the peak and trough extremes, whose height is 2/3 of the peak-to-trough height.
If one of the baselines cannot be identified, the local baseline is set to the found value. If neither baseline can be
identified, then the local baseline is set halfway between the extremes of the local feature's peak and trough.
If baselines can be identified on both falling and rising slopes, the local-feature baseline is an average of the two
baselines and 1 bsep is the distance between them.
If the local feature is the last to be identified before arriving at the end of the region being analyzed, it will not be
possible to identify the trough-to-peak baseline of the following local feature. But when the peak-to-trough
baseline is identified, then these two baselines are assumed to be separated by the same distance as the
baselines for the previous local feature. And if this baseline cannot be identified, then the local baseline becomes
the midpoint of the local peak and trough.
The separation between the baselines (local baseline separation) can also be of interest in determining the
validity of certain measurements.
The following table summarizes the determination of the local baseline and its separation when the local feature is
and is not the last identified before the right parameter cursor:
Local baseline and local baseline separation if last local feature
Baseline identified peak-to-
trough (PTBase)
yes
no
WP700Zi-OM-E-RevA
Local Baseline
(PTBase + [PTBase + previous
separation])/2
midpoint of local peak and trough
Operator's Manual
Baseline Separation
previous local feature's baseline
separation
0
472