17. Add-on Controller
86
Dr. A. Kuntze
I
Gutes Wasser mit System
Robert-Bosch-Str. 7a
40668 Meerbusch
+49 (0) 2150-7066-0 / Fax -60
www.kuntze.com
Start by setting a P controller, then reduce the proportional range until the measured value fluctuates
constantly around the set point. Measure the time between subsequent maximum measured values.
The ideal P range is then 1.66 times the current setting, the ideal integral time is 0.5 times and the
ideal differential time 0.12 times the measured time between maximum values. If the measured value
still oscillates set slightly higher values for P and I and slightly lower values for D..
17.1.5. 3-point controller
Note
Set point S2 cannot be used when S1 is configured as 3-point controller.
Note
Relay 1 is assigned to OPEN and relay 2 to CLOSE.
The 3-point controller is used for actuators that have not only two states (ON and OFF) but three:
OPEN, OFF, and CLOSE, such as motor-operated valves.
Besides set point and controller type you can set the following
parameters:
P range, integral time and differential time
3-point controllers can be configured as PI or PID controller. Settings are the same as described above.
If you set the differential time to zero, the controller type is PI.
Hysteresis
For 3-point controllers you can define a hysteresis to prevent constant movement of the actuator in the
vicinity of the set point. The relay switches only when the difference between set point and measured
value exceeds half the hysteresis value.