Why is a 3-state controller unsuitable for actuator drives?
The modulating controller, like the 3-state controller, has two switching control outputs, which are, however, designed especially for motorized actuator drives, e.g. for opening or closing. If a continuous output signal is required for the 3-state controller in order to maintain a certain output level, we can see that, in the case of the modulating controller, the electrical actuator drive will remain in the position reached when there is no further signal from the controller.
Accordingly, the actuator drive can remain 60 % open, for example, although it is not operated by the controller at this instant.