Operation - Adjustment; Starting Point And Reference Variable - Samson 3761 Mounting And Operating Instructions

Operation – Adjustment
4 Operation – Adjustment
4.1 Starting point and reference
variable
Note!
The positioner is delivered with the default
settings adjusted by the manufacturer.
The pre-determined fitting position of the
tension spring (4) is marked by a dot of
paint and should not be changed.
If the reference variable is, e.g. 4 to 20 mA
(0.2 to 1 bar), the angle of rotation for
opening or closing the valve determined by
the cam disc causes the valve to travel
through its full range.
The starting point is 4 mA (0.2 bar); the up-
per range value is 20 mA (1 bar).
Note!
Zero adjustment is always based on the
valve's closed position. As a result, zero ad-
justment depends on the actuator version
used, e.g. for an actuator with reverse oper-
ating direction, zero must be set to 20 mA
(1 bar) instead of 4 mA (0.2 bar).
The exact starting point is adjusted using
the zero adjuster (3; Fig. 2).
The upper range value is automatically de-
termined by the cam disc's angle of rotation.
If it should be necessary to correct the upper
range value, only slight changes can be
made using the potentiometer span of the
electropneumatic positioner. Turn the poten-
tiometer counterclockwise to reduce the
span and clockwise to increase it.
16
EB 8386 EN
Note!
Electropneumatic positioners with tight-clos-
ing function are equipped with a slide
switch on the printed input circuit board to
activate or deactivate the function.
Important!
Switch off the activation/deactivation func-
tion while adjusting zero. Do not activate
the relevant function on the switch before
zero has been adjusted.
Version without tight-closing function
Potentiometer span
Version with
tight-closing function
Potentiometer span
Fig. 8 · Adjuster
OFF
ON