Siemens SIPART PS2 Series Technical Description page 4

Electropneumatic positioners
SIPART PS2
Technical description
Stainless steel casing for extreme ambient conditions
The SIPART PS2 is available in a stainless steel casing (without
window in the lid) for use in particularly aggressive environments
(e.g. offshore operation, chlorine plants etc.). The device func-
tions are the same as those of the basic versions.
■
Design
The SIPART PS2 positioner is a digital field device with a highly-
integrated microcontroller.
The positioner consists of the following components:
• Casing and cover
• PCB with corresponding electronics with or without communi-
cation through HART
or with electronics for communication in accordance with
- PROFIBUS PA specification, IEC 61158-2; bus-supplied de-
vice, or
- FOUNDATION Fieldbus (FF) specification, IEC 61158-2,
bus-supplied device
• Actuator travel detection system
• Terminal housing with screw terminals
• Pneumatic valve manifold with piezoelectric valve precontrol.
The valve manifold is located in the housing, the pneumatic con-
nections for the inlet air and the positioning pressure on the right-
hand side. A pressure gauge block and/or a safety solenoid
valve can be connected there as options. The SIPART PS2 posi-
tioner is fitted to the linear or part-turn actuator using an appro-
priate mounting assembly. The circuit board container in the
6
casing provides slots for separately ordered boards with the
following functions:
I module:
y
• Position feedback as a two-wire signal 4 to 20 mA.
Alarm module (3 outputs, 1 input):
• Signaling of two limits of the travel or angle by binary signals.
The two limits can be set independently as maximum or mini-
mum values.
• Output of an alarm if the setpoint position of the final control
element is not reached in automatic mode or if a device/fitting
fault occurs.
• Second binary input for alarm signals of for triggering safety
reactions e. g. for blocking function or safety position.
Limit signaling through slot-type initiators (SIA module)
Two limits can be signaled redundantly as NAMUR signals
(EN 60947-5-6) by slot-type initiators. The module also contains
an alarm output (see Alarm module).
Limit value signal via mechanical contacts (Limit value con-
tact module)
Two limits can be signaled redundantly by switching contacts. A
fault message output is also integrated in the module (see alarm
module).
Valid for all modules described above:
All signals are electrically isolated from one another and from the
basic unit. The outputs indicate self-signaling faults. The mod-
ules are easy to retrofit.
Separate mounting of actuator travel detection system and
controller unit
The actuator travel detection system and controller unit can be
connected separately for all casing versions of the SIPART PS2
(except flameproof design). Measurement of the travel or angle
is carried out directly on the actuator. The controller unit can then
be fitted a certain distance away, e.g. on a mounting pipe or sim-
ilar, and is connected to the travel detection system by an elec-
tric cable and to the actuator by one or two pneumatic lines.
Such a split design is frequently advantageous if the ambient
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© Siemens AG 2008
conditions at the fitting exceed the specified values for the posi-
tioner (e.g. strong vibrations).
The following can be used for measuring the travel or angle:
• NCS sensor
• External position detection system C73451-A430-D78
• A commercially available potentiometer (10 kΩ resistance)
(e.g. for higher application temperatures or customer-specific
applications)
The use of linear potentiometers is recommended for very small ac-
tuators with a short valve travel since, on the one hand, the space
required by the linear potentiometer is very small and, on the other,
the transmission characteristic is optimum for a small travel.
Separate connection of actuator travel detection system and controller unit Separate connection of actuator travel detection system and controller unit
Non-contacting position sensor (NCS)
Contact and non-contacting positioning sensor (NCS) for part-turn actu-
ator (left) and for linear actuator 14 mm (0.55 inch) (right)
NCS for travels >14 mm (0.55 inch)