Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 225)

4 Parameters
PC Control / Touch Control
213
Parameters for the predefined titration rates for KFT
Titration rate slow optimal fast
Control range
(Dynamics)
300.0 mV
40.0 μA
100.0 mV
10.0 μA
30.0 mV
5.00 μA
Max. rate 1.00 mL/min maximum maximum
KFT
Min. increment minimum
(= cylinder vol-
ume/10000)
minimum
(= cylinder vol-
ume/10000)
5.00 μL
Editing the parameters for the Stop criterion:
• Stop criterion (d): When the endpoint has been reached and the
stop criterion has been fulfilled the titration is stopped. The titration
can be stopped when a certain (volume) drift has been reached
or after a certain time. If no stop criterion has been selected then
the titration will not be stopped. The Stop conditions (see follow-
ing page) will always ensure a stop, even if the stop criterion has
not been reached.
• Stop drift (d): When the endpoint and the stop drift have been
reached the titration is stopped.
• Delay time (d): When the endpoint has been reached the given
time will be allowed to elapse after the last addition and the titration
will then be stopped.
• Relative stop drift (d): When the endpoint and the sum of the
drift at the start of the titration and the rel. stop drift have been
reached then the titration will be stopped.
You can use the Delay time to calculate the maximum stop drift to be
used in the following way: the size of the last added increment depends
on the volume of the attached exchange unit. With a 20 mL exchange
unit (10'000 pulses per cylinder volume; for KFT command is inde-
pendent of the dosing drive) the smallest possible increment is 2 μL.
With a Delay time of 5 s the last 2 μL of reagent must therefore suffice
for 5 s or longer. This gives a drift of ≤ 2 μL/5 s = 24 μL/min. (The drift
may be smaller than 24 μL/min as we do not know whether the last in-
crement would also have been sufficient for 10 s.) This means that if
you use a 20 mL exchange unit (10'000 pulses per cylinder volume; in-
dependent of the dosing drive) and 5 s switch-off delay then you should
set a value of ≤ 24 μL/min as the stop drift.
Under Titration parameters the parameters for the titration sequence
are edited:
• Titration direction (d): A direction is normally given as stan-
dard. With auto the titration direction is determined from the initial
measured value and the set endpoint.
• Extraction time (d): The titration continues during this time. The
titration is not stopped until the extraction time has elapsed (even