Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 216)

4.1 Titrations
204
PC Control / Touch Control
In the example shown an EP criterion of 20 would make sense if only
the first equivalence point is to be recognized.
Evaluation and equivalence point criterion in the MET mode
The equivalence points (EPs) are localized by a procedure based on
the Fortuin method which has been adapted by Metrohm for numerical
methods. A search is made for the largest measured value alteration
(∆
n
). The exact EP is determined by using an interpolation factor ρ; this
depends on the ∆-values before and after ∆
n
:
V
EP
= V
0
+ ρ ∆V
V
EP
= EP volume, V
0
= total volume added before ∆
n
, ∆V = volume in-
crement, ρ = interpolation factor according to Fortuin
For the recognition of the EPs found the set EP criterion is compared
with the ERC (Equivalence point Recognition Criterion) found. The ERC
is the sum of the measured value alterations before and after the jump:
|∆
n–2
|+|∆
n–1
|+|∆
n
|+|∆
n+1
|+|∆
n+2
|
(In certain cases only three or only a single summand are taken into ac-
count.)
EPs whose ERC is smaller than the set EP criterion will not be recog-
nized. The ERC for each found and recognized EP will be shown under
Results/Curve/EP Details . If you subsequently adapt the EP criterion
so that more or fewer EPs are recognized, you can trigger the re-
evaluation under Results with [Recalculate].