Operation Manual

Continuous valve actuator CHEOPS control
theben
As of: Jul-11 (Subject to change without notice) Page 60 of 71
5.9 Temperature control
5.9.1 Introduction
Cheops Control can be used as a P or a PI controller, although the PI control is always
preferred.
With the proportional control (P control), the actuating value is rigidly adjusted to the
temperature differential.
The proportional integral control (PI control) is far more flexible, i.e. controls more quickly
and more accurately.
To explain the function of both temperature controls, the following example compares the
room to be heated with a vessel.
The filling level of the vessel denotes the room temperature.
The water supply denotes the radiator output.
The heat loss from the room is illustrated by a drain.
In our example, the maximum supply volume is 4 litres per minute and also denotes the
maximum radiator output.
This maximum output is achieved with an actuating value of 100%.
Accordingly, at an actuating value of 50%, only half the water volume, i.e. 2 litres per minute
would flow into our vessel.
The bandwidth is 4l.
This means that the controller will send an actuating value of 100% while the actual value is
smaller than or equal to (211 – 41) 171.
Function:
• Desired filling quantity:
21 litres (= set point value)
• From when should the supply flow gradually be reduced in order to avoid an
overflow? :
4l below the desired filling volume, i.e. at 21l – 41 = 171 (=bandwidth)
• Original filling volume
15l (=actual value)
• The losses amount to 1l/minute