Bronkhorst CORI-FILL - Manual (Page 14)

9.17.075
Bronkhorst Cori-Tech BV
14
7 On-off dosing using a shut-off Valve
Dosing example:
Counter limit = 10.00g.
Measured counter value = 9.98g
Counter value line in FlowPlot = 99.8%
Give a setpoint of any value, a shut-off valve will either be open or closed, so
setpoint value is irrelevant.
Please use a correct and stable inlet pressure
Because of the self learning principle (overrun correction) the requested
counter value will always be very accurate.
The Counter control gain option has no influence on dosing with a shut-off
valve. This formula is explained in section 8.
Overrun correction (on-off control):
A correction value between 0 and 1 can be entered. Therefore, when a value
is entered, the system will close the valve a fraction earlier or later,
depending on the overrun (or underrun). An overrun correction of 0.8 has
proven to be a proper functioning value. The closing value for the valve is
calculated by the following formula:
Closing value = Limit value – (Overrun correction *
(Last actual dosing value – Limit value)).
For example: if the last limit value for the dosing was 10g and the actual measured value was 10.50g, considering a overrun
correction factor of 0.8, for the next dosing the valve will close at: 10 – ( 0.8 * (10.5 – 10) ) = 10 – 0.40 = 9.60g
This correction is a continuous process, therefore it ensures that the requested dosing value will come to 10g.
Lower correction values can be used to filter instabilities in supply pressures, this will result in more cycles before the requested
batch is reached. Higher values result in fast correction and less cycles before final batch is reached.
PID settings can't be used in combination with shut-off valves!