Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 212)

4.1 Titrations
200
PC Control / Touch Control
The conditions for terminating the titration are defined under Stop con-
ditions :
• Stop volume (d): Stops when the preset volume (including start
volume) has been added since the start of the titration. The stop
volume should be adapted to suit the sample weight or the titration
vessel size.
• Stop measured value (d): Stops when the preset value for a meas-
uring point has been exceeded or undercut since the start of the ti-
tration.
• Stop EP (d): Stops when the preset number of equivalence points
has been found.
• Volume after EP (d): When the number of equivalence points de-
fined under Stop EP has been found this volume will be added. In
this way the curve can be continued after the equivalence point has
been reached.
• Stop time (d): Stops when the preset time (including start condi-
tions) has elapsed since the start of the titration.
If several stop conditions have been set then the first criterion to be ful-
filled will stop the titration.
• Filling rate (d): Rate at which the dosing cylinder is refilled after
the titration. The maximum filling rate depends on the cylinder vol-
ume of the exchange or dosing unit used (see Section 3.8.6).
Under Potentiometric evaluation the parameters for the evaluation
of the titration curve, i.e. for automatic equivalence point recognition,
are edited:
• EP criterion (d): The set equivalence point criterion is compared
with the ERC (Equivalence point Recognition Criterion) which has
been found. Equivalence points whose ERC is smaller than the set
EP criterion will not be recognized (see p. 203 and p. 204). The de-
fault value is suitable for most titrations.
• EP recognition (d): This parameter allows you to filter out the
endpoints you are looking for. Either all the equivalence points can
be recognized, or only those which meet particular criteria: the
greatest (only the EP with the largest ERC, i.e. the steepest jump),
the last (only the last EP to be found), ascending (only EPs with a
positive titration curve slope), descending (only EPs with a negative
titration curve slope).
• Set windows: Up to nine ranges (windows) can be defined on both
the measured value axis as well as on the volume axis. Only equiva-
lence points in the preset windows will be recognized and num-
bered according to the window (e. g. EP2 in window 2).
A window defines a range in which an equivalence point is expected.
Equivalence points outside this range will not be recognized. Setting
windows is advisable when interference and unnecessary equivalence
points are to be suppressed. The list of windows is opened with [Set
windows] .