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Searching For and Computing Peaks

Last Modified: September 3, 2019

After enabling at least one FFT channel and markers, you can use the peak search functions to locate peaks. Peaks are the samples for which the amplitude rises and falls around a threshold. You can move the selected marker to the highest peak, the next highest peak, or an adjacent peak to the left or right of the marker. You can configure the peak threshold and excursion settings by selecting the cog icon next to the peak search functions.

Computing Peaks Using Peak Threshold and Excursion

The peak threshold is the minimum amplitude level a sample must rise above to be considered a peak. If peak threshold is enabled but peak excursion is not, every amplitude measurement above the threshold is considered a peak. Set the peak threshold from the peak search settings.

Peak excursion specifies the minimum amplitude variation required in a signal to be considered as a peak. Peak excursion is always specified with respect to a threshold value. A signal must rise and fall above the threshold level by at least the peak excursion value to be considered as an eligible peak.

The following figure shows how to identify a valid peak that meets excursion criteria:

Peak 1 rises and falls by at least the peak excursion value above the threshold. Hence, it follows the excursion criteria.

Peak 2 is above the threshold level, but it does not rise and fall by the excursion value above the threshold level. Hence, it does not satisfy excursion criteria.

Peak 3 rises above the threshold value by at least the excursion value, but it does not completely fall by the excursion value. The signal rises and crosses the Peak 3 amplitude level. Hence, it is not an eligible peak.

Peak 4 rises and falls by at least the peak excursion value above the threshold. Although during the rise it slightly falls (Peak 3) the net rise from the threshold level exceeds the excursion value. Hence, it is considered an eligible peak.

Peak 5 is below the threshold level. Hence, it is not detected as a peak.

Peak 6 rises by at least the peak excursion value above the threshold. During the fall, the signal slightly rises (as Peak 7), but it does not rise above peak 6 amplitude level before falling again. The total fall, which starts at the peak 6 amplitude level, is more than the excursion value. Hence, it is an eligible peak.

Peak 7 falls by the excursion value, but it does not rise by the excursion value. Hence, it does not satisfy excursion criteria.


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