Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 219)

4 Parameters
PC Control / Touch Control
207
Parameters for the predefined titration rates for SET
Titration rate slow optimal fast
Control range
(Dynamics)
5.000 pH
300.0 mV
40.0 μA
2.000 pH
100.0 mV
10.0 μA
0.500 pH
30.0 mV
5.0 μA
Max. rate 1.00 mL/min 10.00 mL/min maximum
SET
Min. rate 5.00 μL/min 25.00 μL/min 50.00 μL/min
Optimizing the control parameters
Reagent addition takes place in three phases during the titration:
• Initial addition: during this phase the dosing rate increases con-
tinuously. It starts with the Minimum rate and increases to the
Maximum rate .
• Continuous addition: addition is carried out at the Maximum rate
until the control range is reached.
• Control range: in this range addition is finely controlled. Shortly
before the endpoint is reached addition is only carried out at the
Minimum rate.
t/s
EP
Control
range
Continuous
addition
Initial
addition
V/mL
V/mL
U/mV
Fig. 4.8: Reagent addition during endpoint titrations with SET
Set a large Control range for steep curves and a small control range
for flat ones. A good approximation for the start of the control range is
given by the point where the tangents intersect: