Bronkhorst CORI-FILL - Manual (Page 18)

9.17.075
Bronkhorst Cori-Tech BV
18
8 Proportional filling
In the “Alarm & Count” tab, the counter setting can be found. The counter will count the total amount of flow passing through the
instrument. The counter has three modes: [Off], [Up] and [Up to limit]. For filling applications, the [Up to limit] has to be selected.
In order to perform a dosage a setpoint value (e.g. 100%) has to be selected. The setpoint value is related to the full scale value.
Setpoint can be changed once the limit has been (or will be) reached. By enabling [new setpoint on limit] and set it at 0.0%, the
dosing set-up is created. Select [reset counter] to perform a dosage. (When the desired limit has been reached, setpoint will be set
to zero).
Counter control gain (proportional filling):
In this mode the PID-controller will be used. This function will work as follows:
The counter starts running up to limit until a certain moment where the controller
starts to slow down. This is needed in order to approach the limit carefully which will
avoid overshoots. The point of slowing down can be set by means of counter control
gain. This value can be changed from 1…100.
Flow value where counter will start to force the setpoint down can be calculated as
follows:
(1 - 1/x ) * 100%. (x = counter control gain value).
In the example to the left, the counter control gain = 2, which means that setpoint
value will go downwards after reaching 50% of the limit (10 g). So at 5g, the counter
will force the controller to decrease its setpoint. Setpoint will decrease down to 2%
(automatically controlled by an additional P- controller for the counter). The last part
of the batch will be dosed at 2% flow rate of the capacity. An example is shown at the
following page.
Note: Fast and accurate proportional filling is possible, therefore it is important to set a few controller options, such
as FS value, counter control gain and the PID-Kp value. Please see section 8.2 & 8.3 for controller options and
findings in practice.
Counter control gain (X) Counter value where controller will slow down
0 No slowing down; controller stops if limit has been reached
1 0%, so immediately when counter starts running
2 50% of max. limit of counter
3 67% of max. limit of counter
4 75% of max. limit of counter
5 80% of max. limit of counter
10 90% of max. limit of counter
50 98% of max. limit of counter
100 99% of max. limit of counter
Please try to make sure that the last phase of dosing will be performed at 2% setpoint, otherwise there could be an
overdose. If this cannot be avoided or when dosing at 2% will still give an overdose, you might consider for enabling
the overrun correction. Both mechanisms can be active at the same time with proportional filling.