Metrohm 746 VA Trace Analyzer - Manual (Page 283)

5.6 Method Specifications
746 VA Trace Analyzer / 747 VA Stand
5-132
Parameter Range; Default value / Meaning
U.width max (U.width min)...400 mV; 200 mV
Maximum peak width
Maximum peak width for the assignment of a peak or a wave to a
substance. The peak width
aU.width estimated in a first approxima-
tion must be smaller than U.width max for the substance to be
recognized (see adjacent diagram and section 6.6).
I.threshold 100...5000 pA; 200 pA
Limiting current value
Limiting current value for the assignment of a peak or wave to a
substance (for all measurement modes with the exception of
PSAMODE). With the aid of the 1
st derivative of the peak curve (or the
2
nd
derivative of the wave curve), the difference ∆
minmax
is multiplied
with an empirical factor f
MM
dependent on the measurement mode to
determine the estimated peak height approx.peak . This estimated
value must be larger than I.threshold for the substance to be
recognized (see also section 6.6).
With non-gaussian shaped peaks, the peak height approx.
peak estimated from the derivative can differ greatly from
the actual peak height I.peak . It may be necessary to
modify I.threshold for the results to be displayed or
suppressed in the desired manner.
aU.width
U.width min
U.width max
U.verify ± U.tol
aU.peak
approx.peak =
aU.max aU.min
I.threshold
I
dI/dU
U
U
The substance recognition is
based on the recognition
parameters specified for the
individual substances. The
following conditions must be
met for a detected peak to
be assigned to a substance:
1. aU.peak =
U.verify
±± U.tol
2. aU.width > U.width min
aU.width < U.width max
3. approx.peak >
I.threshold
∆
minmax
∆
minmax
× f
MM
estimated
gaussian
peak