Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 224)

4.1 Titrations
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PC Control / Touch Control
4.1.3 Karl Fischer titrations (KFT)
Under Start conditions the parameters for the addition of the start
volume of titrant and for measuring the initial measured value are ed-
ited. These conditions must be fulfilled before a titration can be started.
• Pause 1 (d): Waiting time, e. g. for electrode equilibration, before
the start volume is added.
• Start volume (d): Volume which is added added before the start of
the titration. Under Dosing rate (d) the rate at which the start vol-
ume is added is entered.
• Pause 2 (d): Waiting time which is allowed to elapse between add-
ing the start volume and starting the titration.
Parameters for the Initial measured value:
• Signal drift (d): Drift, i.e. alteration of the measured value per
minute, which has to be reached before the measured value will be
accepted.
• Waiting time min. (d): The measured value is not accepted until
the minimum waiting time has elapsed, even if the measured value
drift has already been reached. The minimum waiting time is only
important for drift-controlled measurements.
• Waiting time max. (d): If the signal drift is switched off or has not
yet been reached then the measured value will be accepted after
the maximum waiting time.
Editing the Control parameters for the endpoint:
• Endpoint at (d): Measured value for the end-point.
• Titration rate (d): Three predefined sets of parameters can be
selected for the titration rate (see Table on following page). If indi-
vidual titration parameters need to be adapted then select the set-
ting User and edit the individual titration parameters under User-
defined parameters .
Editing the User-defined parameters:
• Dynamics (d): The dynamics defines the measured value range
(control range) before the given endpoint. In the control range dos-
ing is controlled by the minimum increment. The closer the end-
point, the slower the dosing until the minimum increment has been
reached. The larger the control range, the slower the titration. Out-
side the control range dosing takes place at the maximum rate.
• Maximum rate (d): Rate at which dosing takes place outside the
control range. The maximum rate depends on the cylinder volume
of the exchange or dosing unit used (see Section 3.8.6).
• Minimum increment (d): This parameter determines the volume
steps at which addition takes place right at the start of the titration
and in the control range at the end of the titration. It has a deci-
sive influence on the titration rate and therefore on the accuracy.
The smaller the selected minimum increment, the slower the titra-
tion.