Operation manual Profibus PBD 100
23.07.2007
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Figure D: Modulating duty: Nominal operation after 50 %
Overrun (inner dead band)
The inner dead band determines the switching-off point of the actuator. The tripping point in both directions can be set via the parameters 12
and 13 (page 18), so that the actuator stops as close as possible to the nominal value.
Max. error (outer dead band)
The outer dead band determines the switching-on point of the actuator. If the error or a change in nominal value is higher than the max. error
set with parameter 14 (page 10), the motor is started.
The parameter must be set sufficiently high to ensure a stable function of the positioner. If the value is set too low, the
number of starts is likely to be too high. Thus, the end of the lifetime of the actuator and valve will be reached sooner.
Dead time (t-off)
The dead time prevents the operation to a new nominal position within a pre-determined time. The time can be between 0 and 1 minute and
is set in parameter 11.
It must be ensured via the controls that the maximum number of starts of the actuator is not exceeded. This can be
achieved by setting the parameter 11 to a sufficiently high value.
9.3
Stepping mode
Stepping mode requires a position transmitter (option).The stepping mode slows down the operating time for a part or all of the travel.
Setting of operation and pause times
The operation and pause times (stepping times) in opening or closing direction are set with the parameters 27 to 33. An individual operation
and pause time can be set for each direction.
Indication of operation in stepping mode
The states of the operation in stepping mode are indicated by the bits 2 and 3 in byte 7 of the process representation output.
Max.
error
=1 %
outer dead band
Overturn
Nominal value
reached
Motor is switched off
CLOSED 0 %
Nominal 50 %
value
49,5 %
49 %
51,5 %
51 %
OPEN 100 %
Position of actuator
