Peak
The term peak comes from English and means 'summit, peak, peak value'. In measurement technology and stochastics , a peak is used to denote a significant peak value .
If you plot measured values in a diagram in a vertical direction (ordinate, y-axis) against time, location or another variable (e.g. wavelength ) as the horizontal axis (abscissa, x-axis), increased measured values appear as They are also called peaks. For them, on the one hand the x-value of the maximum is interesting, but also mostly either the height of the apex or the area under the peak. In practice, the measured values to the left and right of the peak are usually not zero, but the peak is a clear rise and fall again (deflection) of the measuring signal above the background noise .
Examples:
- Chromatography ( gas chromatography , high-performance liquid chromatography ): each peak in the chromatogram corresponds to a detected substance
- every “photopeak” in a gamma spectrum corresponds to a proven gamma spectral line
- in economic statistics , for example, Peak Oil , the point in time when global oil production peaks
- In acoustics and audio technology, the peaks are called the level and are measured with the level meter (peak meter), which shows the maximum peak over a measuring period
The measures for the intensity of the peak are generally the factors that are also used as a basis for normal distribution , in particular values that are used to evaluate the time of the peak:
- the crest factor, a measure of the ratio of peak level to mean value ( effective value in electrical measurement technology)
- or for negative peaks with only positive scales, otherwise
- the tailing factor (' sidecut ' of the tip, width of the peak), at around 5% or 10% of the peak height, which is also a measure of the symmetry of the peak
- or with y a , y b as the distance of the underlying percentage from peak value