
4.3.2Setting actuator version
“Stem extends”
Note!
To ensure that the total closing force of the
actuator can be effective in the control
valve, the diaphragm chamber must be
completely vented at the lower range value
of the reference variable (operating direc-
tion <<) and at the upper range value (oper-
ating direction <>).
Therefore, set input signal to a slightly in-
creased starting point of 4.5 mA when the
operating direction is direct << and to a
slightly lowered starting point of 19.5 mA
when the operating direction is reverse <>.
This applies in particular to controllers and
control systems whose output signal is lim-
ited to a range of 4 to 20 mA.
Starting point (zero) e.g. 4.5 mA
1. Turn the zero adjustment screw (4) until
the plug stem just begins to move from
the resting position (observe plug stem
with travel indicator).
2. Reduce the input signal on the ammeter
and increase again slowly. Check
whether the plug stem starts moving at a
starting point of 4.5 mA and, if neces-
sary, correct.
Upper range value (span) e.g. 20 mA
3. After the starting point has been ad-
justed, increase the input signal. The
plug stem must be motionless at an up-
per range value of exactly 20 mA and
therefore already moved through 100 %
of its travel range (watch the travel indi-
cator at the valve!). If the upper range
value is incorrect, the pin (2) must be
moved as follows in order to correct the
signal:
4. Move pin to:
End of lever –> to increase travel
Pivot –> to reduce travel
Whenever you correct the input signal,
re-adjust zero afterwards. Subsequently,
check the upper range value.
Repeat until the two values match.
4.3.3Setting actuator version
“Stem retracts”
Note!:
For actuator version "Actuator stem re-
tracts", the diaphragm chamber must be
loaded with a pressure that is capable of
tightly closing the control valve, even with
prevailing upstream pressure in the plant.
This concerns an upper range value of the
input signal corresponding to 20 mA (direct
operating direction <<) or a lower range
value corresponding to 4 mA (reverse oper-
ating direction <>).
The required signal pressure is indicated on
the adhesive label on the positioner or is
roughly estimated as in section 3.2.2 on
page 11.
Starting point (zero) e.g. 20 mA
1. Adjust the input signal to a starting point
of 20 mA on the ammeter.
Turn the zero adjustment screw (4) until
the control valve just begins to move
from the initial position.
16 EB 8359-2 EN
Operation