Operation Manual

Continuous valve actuator CHEOPS control
theben
As of: Jul-11 (Subject to change without notice) Page 61 of 71
5.9.2 Response of the P-control
Max. 4l/Min.
Bandwidth
Set point value
Actual value
17l
21l
15l
Losses
1l/Min
A filling volume of 15l gives rise to a control deviation of 211 – 151 = 61
Because our actual value lies outside the bandwidth, the control will control the flow at 100%
i.e. at 4l / minute
The supply quantity (actuating value) is calculated from the control deviation
(set point value – actual value) and the bandwidth.
Actuating value = (control deviation / bandwidth) x 100
The table below shows the response and therefore also the limits of the P-control
Filling level
Actuating value
Supply
Losses
Increase in filling
level
15l
100%
4 l/min
1 l/min
3 l/min
19l
50%
2 l/min
1 l/min
20l
25%
1 l/min
0 l/min
The last line indicates that the filling level cannot increase any further, because the flow
allows only the same amount of water to flow in as can flow out through loss.
The result is a permanent control deviation of 11 and the set point value can never be reached.
If the loss was 1l higher, the permanent control deviation would increase by the same amount
and the filling level would never exceed the 19l mark.