Owner manual

6 Data processing and evaluation
746 VA Trace Analyzer / 747 VA Stand
6-14
6.7.3 Baselines for peaks
With peak-shaped curves which have been recorded with the DPMODE,
SQWMODE, AC1MODE, DCTMODE (with SSWEEP) and CYMODE (with 1 ramp)
measurement mode, the following possibilities exist for calculation of the baseline:
• Type = linear, Scope = whole
The baseline of type linear is determined using the tangent method. With
the peak base points dU.front and dU.rear determined beforehand as a
basis, an iterative search is made within a fixed range for identical slopes. The
range for the tangent search is ca. 20 mV outward and inward up to 1 point
before the peak maximum.
If two points with an identical slope are found, the two points of tangency are
connected to give the linear baseline. If no common slope is found, the linear
baseline is drawn directly through the two base points.
Instead of being deter-
mined automatically, the
two base points dU.front
and dU.rear can also be
entered manually either by
numeric entry or by shift-
ing using the cursor keys
(see "CURVES", section
5.5.3). In contrast, the two
slopes S.front and
S.rear are always calcu-
lated automatically, a nu-
meric entry here is ig-
nored.
linear, whole
dU.front dU.rear
• Type = linear, Scope = f.half/r.half
The baseline of type linear, f.half is determined only by starting from the
peak front half, that of type linear, r.half only by starting from the peak
rear half. In the first case, the baseline is given by the tangent with the slope
S.front at the base point dU.front, in the second case by the tangent with
the slope S.rear at the base point dU.rear.
The two base points dU.front and
dU.rear as well as the two slopes
S.front and S.rear can also be
entered manually instead of being
determined automatically.
linear, f.half linear, r.half
• Type = linear, Scope = f.double/r.double
This type of baseline is used for the evaluation of overlapping peaks; for the
1
st
peak the type linear, f.double must be used and for the 2
nd
peak the
type linear, r.double. The baseline is calculated in exactly the same man-
ner as for linear, whole using the tangent method. With the previously de-
termined peak base points dU.front for the 1
st
peak and dU.rear for the 2
nd
peak as a basis, an iterative search is made within a fixed range for identical
slopes. The range for the tangent search is ca. 20 mV outward and inward up
to 1 point before the corresponding peak maximum.
Point of tangency
(rear)
Subtracted
curve
Base point
(front)
Range for
tangent search
Range for
tangent search
Base point
(rear)
Point of tangency
(front)