17. Add-on Controller
85
Dr. A. Kuntze
I
Gutes Wasser mit System
Robert-Bosch-Str. 7a
40668 Meerbusch
+49 (0) 2150-7066-0 / Fax -60
www.kuntze.com
17.1.3. PI controller
The PI controller is a P controller with additional I function. The I function sums up the previous dosing,
so that the controller output drops to zero only after the measured value already exceeds the set point.
This eliminates in applications with constant inflow the otherwise unavoidable control deviation.
Besides set point and controller type you can set the following
parameters:
P range
For settings and information refer to P controller.
Integral time
The shorter the integral time, the stronger the I function.
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 2.2times the current setting and the ideal integral time is 0.85 times the
measured time between maximum values. If the measured value still oscillates set slightly higher values.
17.1.4. PID controller
The PID controller is a PI controller with additional D function. The d function acts swifter and
compensates the inertia of the I function. This allows the controller to react faster to large control
deviations.
Besides set point and controller type you can set the following
parameters:
P range
For settings and information refer to P controller.
Integral time
For settings and information refer to PI controller.
Differential time
The higher the differential time, the stronger the D function.