Siemens 6DR55 Series Manual page 26

Design and method of operation
24
The limit value alarms are output by the alarm option module which can
monitor and report the function of the positioner and the actuator
additionally through a fault message output. The value of the control
difference dependent on the travel time is monitored in automatic
mode. The fault signal is always set when the control error cannot be
leveled after a certain time because for example the valve is blocked or
the mains pressure is insufficient. The three binary outputs are
implemented as semiconductor outputs and are error self--reporting,
i.e. the outputs respond even when the power supply fails or the
electronics are defective.
The actuator can also be blocked or driven to its final positions
depending on the configuration for example by an external event via a
binary input (BI2) on the alarm module.
If you require electrically independent limit value messages from the
standard controller, you will have to use the SIA module with the slot
initiators instead of the alarm module.
To be able to use the positioner with a variety of different part-turn and
linear actuators, it has a friction clutch and switchable gearing.
The switchable gearing allows you to adjust the positioner for small and
large lifts. You can switch using the yellow switch (9, Fig. 8, page 25)
between 33_ (as delivered) and 90_.
The friction clutch (8, Fig. 8, page 25) allows you to set the working
range, particularly for linear actuators, after installation. You thus do not
have to ensure symmetrical mounting during the installation.
As it is not allowed to open the housing of an explosion proof version in
a potentially explosive atmosphere, the shaft has an externally fitted,
additional friction clutch (8, Fig. 9, page 26).
NOTICE
for the explosion proof version:
Only adjust the outer friction clutch (8, Fig. 9, page 26). The internal
friction clutch (9, Fig. 8 page 25) is fixed and, for the explosion proof
version, must not be adjusted.
SIPART PS2 PA Manual
A5E00127926--05