Physical
stroke
x [%]
Unlimited stroke
Limited stroke
Set value w [%]
Max
Pos
Min
Pos
If parameter 23: CLOSETIGHT is activated the
actuator is vented at a set value of < 0.5 %, even if
there is a set MIN POSITION of, for example, 10 %.
With a set value > 1.5 % the actuator is moved
back to 10 %.
With a set value > 99.5% the actuator is opened
completely, even if the MAX POSITION is set to,
for example, 90 %. With a set value < 98.5 % the
actuator is moved back to 90 %.
23: CloseTight
'Close tight' variables
With this function the valve can be moved into the seat using
the maximum possible actuating force (spring force). The
close tight function can be activated for one end or both end
positions. CLOSE TIGHT becomes eff ective when the set
value falls below 0.5 % or exceeds 99.5 %.
The switch back hysteresis is 1 %.
Stroke x [%]
Set value w [%]
24: SETP DIRECTN
Set value direction
Setting the set value direction serves to reverse the direction
of the set value. It is mainly required for split-range operation
and for single acting actuators with the fail safe "OPEN" setting
(control function 2).
Stroke x [%]
Set value w [%]
Control function 2
Control function 2
Control function 1
NORMAL
NORMAL
INVERSE
OPEN
CLOSED
25: SETP RAMP
Set value ramp
The set value ramp is eff ective during automatic operation and
limits the speed of change of the eff ective set value. When
switching over from manual to automatic operation the eff ective
set value is matched to the set value on the unit via the set
value ramp.
In the position SETP RAMP = auto the slower of the two travel
times which have been established during initialisation is used
for the set value ramp.
26: SPLIT START
Set value split range start
27: SPLIT END
Set value split range end
Parameters 26 and 27 in conjunction with parameter 24 serve
to limit the eff ective set value range. In this way split range
tasks with the curves
rising / falling
falling / rising
falling / falling
rising / rising
are resolved.
Stroke x
Set value
w
Set value range
Positioner 1 Positioner 2
Set value range
The diff erence between SPLIT START and SPLIT
END values must be > 10 %.
28: SETP FUNCTN
Set value function
With this function non-linear valve characteristics can be
linearised and with linear valve characteristics any fl ow
characteristics can be reproduced.
Four valve characteristics are stored in the unit:
equal-percentage 1 : 25
(in CLOSED position valve remains 4 % open)
equal-percentage 1 : 50
(in CLOSED position valve remains 2 % open)
linear
free
When free is selected at 30: a characteristic with 11 calibration
points can be entered.
30: FREE 0 %
.
.
.
40: FREE 100 %
At gaps of 10 % a fl ow characteristic value can be allocated to
the set value calibration point concerned. These points make a
traverse with 10 straight lines, which then provides a pattern of
the valve characteristic.
Entering the set value calibration points is only
possible at 28: SETP FUNCTN = free.
To Next Page
