Bronkhorst®
Instruction Manual mini CORI-FLOW ML120
9.17.097G
56
Lower values start the control gain phase earlier, which can lead to exceptionally long dosing times. A minimum value of
10 is recommended (corresponding to 90% of the batch delivered). If this leads to batch size overshoot, consider lowering
the maximum capacity (rather than lowering
Counter control gain
).
The following digital parameters are involved in adjusting the flow progress during each batch:
Name
Process/
Parameter
Modbus
register no
Value
Purpose/Remarks
Capacity (21)
1/13
33129…
33130
as required
·
set maximum dosing flow
·
analog output signal is re-scaled accordingly (20 mA corresponds
to 100% FS)
Counter Controller Gain
(275)
104/11
59481…
59482
as required prevent batch size overshoot by reducing flow when approaching
configured batch size
Optimizing controller
The PID controller settings of the instrument are optimized before shipping. Generally, changing these settings is strongly
dissuaded. However, for proportional batch dosing, adjusting some of the PID-parameters slightly might prove useful to
improve response performance and dosing accuracy.
In FlowPlot, the controller settings are located on the
Controller
tab of the
Instrument Settings
.
1. A control valve (or pump) needs a minimum electrical
current (threshold) to open (or start running). Normally,
when opening the valve, the current is increased gradually,
until the threshold is reached and the valve opens. The
time to reach the threshold (dead time) can be minimized,
by specifying a starting power/current, just under the
threshold. This shortens the valve response time, because
the starting power is immediately applied when the valve
is opened (instead of gradually).
2.
Setpoint slope
can be used to smooth 'nervous' behavior of
the PID controller (reduce setpoint overshoot or
undershoot), but with proportional batch dosing, this
might lengthen the dosing time unacceptably. The
recommended value for
Setpoint slope
is 0.
3. Dosing speed can be increased, by optimizing the PID
settings of the controller. Be aware, however, that even
small changes might result in violent reactions and
unstable control behavior. The recommended values are
shown in the image to the right and in the table below.
·
The required power to open the valve can be determined automatically, by clicking the
Learn open
button. Note that
this only works by (temporarily) disabling the counter(
Counter mode
·
If necessary, the PID dials can be re-scaled by clicking on a scale value and entering a new value.
