Metrohm 751 GPD Titrino - Manual (Page 71)

2.6. Parameters, key <PARAM>
751 GPD Titrino
68
Measured value ramp
In DOC the set value of a measured quantity is changed linearly from a start value to a
final value during a preset sweep time (measured value gradient). The reagent addition is
controlled so that the current measured value follows the nominal value. DOC is stopped
when the sweep time is at an end and (if the measured value monitoring is active) when
the current measured value corresponds to the end of the ramp.
The control deviation nominal-actual value can be kept very small by a suitable choice of
parameters and reagent concentration.
If the current measured values is
still outside of the control range,
the dosing rate is mainly given
by the parameter "max.rate".
If the current measured values is
inside the control range, the
dosing rate is mainly given by
the parameter "min.rate".
If a T sensor is connected, the temperature is measured continuously and pH values
compensated accordingly.
Measuring point list and monitoring
• Measured points are entered in the measuring point list at the preset time interval. The
inputted times represent the clock time. This must be distinguished from the
dispensing time: The dispensing time does not include any wait times which can arise
in refilling, hold or wait as a result of limit value violations.
• If one (or more) entries occur in the time during refilling, one measured point is entered
immediately after the refilling. The time reference otherwise remains unchanged,
however.
• The measuring point list always includes the values "time" and "volume". If monitoring
of measured values and/or temperature is active, the corresponding values are also
entered.
• The "mess." column shows a message if a limit value was violated in the last time
interval, see example of a measured point list on page 53. "*" is also used in this
column to mark when the dispensing was interrupted: refilling, action "wait" or "hold" on
limit value violation or manual <HOLD>.
• The volume of the last measured point entry can differ from the final volume as time
may have elapsed between the last entry and the actual stop.
• If the last measured value is important, set the sweep time 1 s higher than the last
expected measured value, i.e. sweep time = (time interval*number meas.values)+1.
Ende
Start
U/mV
t/s
EP "running"
V/ml
t/s
Control range
Sweep time
Here the final
meas.val. was
reached