892 J006 MNAH | PGC5000 G EN 2 | 91
stray above this threshold, the user is given the option to multiply this value by a threshold factor.
The result gives an envelope above which the second derivative algorithm decides that a peak may be
starting. The threshold factor TCF can be adjusted when the sequence TCF is entered. The larger the
factor entered at the setup screen, the larger a deviation from baseline is required before a peak is
assumed.
5.4.3 Single peak integration range
The integration range of a peak is defined to be the point at which the signal first emerges above the
threshold and the point at which it first disappears below the threshold (see Figure 5-8).
Figure 5-8: Single peak
5.4.4 Multiple peak integration range
A multiple peak cluster is where the signal does not drop back to the threshold in the valley between
peaks (Figure 5-9). The peaks are cleaved by a line dropped from the lowest point of the valley
perpendicular to the baseline (perpendicular drop). Integration for the first peak of the mountain
range is from the emergence point to the first perpendicular drop. A middle peak is integrated from its
left perpendicular drop to its right perpendicular drop. The last peak is integrated from its left
perpendicular drop to the return to threshold.
Figure 5-9: Multiple peaks
5.4.5 Tangent skim
Whenever a bump or small peak appears on the trailing side of a much larger peak, the smaller peak
can be cleaved from the larger by a technique called tangent skim (see Figure 5-10). If a valley is
present between the two peaks, a tangential line is drawn from a point of the falling curve near the
bottom of the valley before the smaller peak to the first point on the falling curve after the smaller
peak that would also be tangential. Tangent skimming is automatically chosen when the ratio of peak
heights from the bottom of the valley between them exceeds ten.
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