Positioner; Position Transmitter; Resistance Transmitters; Mechanical Limit Contacts - Samson 3274 Mounting And Operating Instructions

Design and principle of operation
3.3.1

Positioner

The positioner compares the 0/4 to 20 mA
or 0/2 to 10 V control signal issued by the
controller with the position of a potentiome-
ter which is proportional to the travel. This
results in an output signal of 0/4 to 20 mA
or 0/2 to 10 V.
3.3.2

Position transmitter

In the version with three-step control, a po-
tentiometer (0 to 1000 Ω) is used to issue a
0/4 to 20 mA or 0/2 to 10 V output signal,
which is proportional to the travel.
3.3.3

Resistance transmitters

An actuator can be equipped with two resis-
tance transmitters. A segment gear is driven
by a shaft. An easily adjustable transmission
mechanism including a twin pinion ensures
that the angle of rotation remains the same
for rated travels of 15 and 30 mm.
3.3.4 Mechanical limit con-
tacts
The actuators can be fitted with a maximum
of three mechanical changeover switches,
which are actuated by continuously adjust-
able cam disks. The motor is switched off by
force-dependent fixed switches in the actua-
tor housing (1).
Actuators with fail-safe action only have one
force-dependent switch since these actuators
are only moved in the other direction by the
force of the springs (5.7 and 5.8).
10
3.3.5

Priority circuit

The version with positioner is fitted with a
priority circuit which is activated at terminals
82 and 83 (see section 7.1.1).
3.3.6

Heating

For low ambient temperatures, the actuator
can be delivered with heating with two heat-
ing resistors in the oil reservoir. The heating
is activated by thermostats when the oil tem-
perature falls below –10 °C and deactivated
again when the oil reaches a temperature of
0 °C. It is connected internally to the power
supply and cannot be retrofitted.
Note
To ensure that the heating can be activated
at temperatures below 0 °C, the power sup-
ply must be applied to the actuator continu-
ously (at least two hours before start-up in
temperatures within the specified range).
EB 8340 EN