DATA COMPUTATIONS C-3
MON2000
JULY 2010 Peak Detection
Having initiated a peak search by turning
Inhibit off, the 2350A Controller performs a
point by point examination of the signal slope.
This is achieved by using a digital slope
detection filter which is a combination low pass
filter and differentiator. The output of this
detector is constantly compared to a system
constant entered by the operator called Slope
Sensitivity. A default value of eight is assumed
if no entry is made. Lower values make peak
onset detection more sensitive and higher
values make detection less sensitive. Higher
values (20 to 100) would be appropriate for
noisy signals, e.g. high amplifier gain. Peak
termination is determined by the same
application of this detector to the signal, but in
the reverse sense. Onset is defined where the
detector output exceeds the baseline constant,
but termination is defined subsequently where
the detector output is less than the same
constant.
Sequences of fused peaks are also
automatically handled. This is done by testing
each termination point to see if the region
immediately following it satisfies the criteria of
a baseline. A baseline region must have a slope
detector value less than the magnitude of the
baseline constant for a number of sequential
points. When a baseline region is found, this
terminates a sequence of peaks. A zero
reference line for peak height and area
determination is established by extending a
line from the point of the onset of the peak
sequence to the point of the termination. The
values of these two points are found by
averaging the four integrated points just prior
to the onset point and just after the
termination points respectively.