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| Separate connection of actuator travel
detection
system and |
Non-contacting position sensor (NCS) |
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Contact and non-contacting positioning sensor (NCS) for part-turn actuator(left) and for linear actuator (right) |
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NCS for travels >14 mm |
The actuator travel detection unit consists of a non-
contacting position sensor instead of a potentiometer.
All coupling elements are omitted such as coupling
wheel and driver pin with part-turn actuators or lever
and pick-up bracket with linear actuators.
This results in:
• Even greater resistance to vibration and shock
• No wear of sensor
• Problem-free mounting on very small actuators
• Negligible hysteresis with very small travels.
The sensor does not require an additional power supply, i.e.
SIPART PS2 (not for EEx d version) can be operated in a 2-wire
system. The NCS (Non Contacting Position Sensor) consists of
a potted sensor housing which must be mounted permanently
and a magnet which is mounted on the spindle of linear actu
ators or on the shaft butt of part-turn actuators. For the version
for travels |
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Design
The SIPART PS2 positioner is a digital field device with a highlyint
egrated microcontroller.
The positioner consists of the following components:
• Casing and cover
• PCB with corresponding electronics with or without communic-
ation through HART
or with electronics for communication in accordance with
PROFIBUS PA specification, IEC 61158-2; bussupplied device,
or Foundation Fieldbus (FF) specification, IEC 611582, bussupplied
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 conn-
ections 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 position-
er is fitted to the linear or part-turn actuator using an appropriate
mounting assembly. The circuit board container in the casing pro
vides slots for separately ordered boards with the following func
tions:
Iy module:
• 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 minimum
values.
• Output of an alarm if the setpoint position of the final control
element is not reached in automatic mode or if a device fault
occurs.
• Second binary input for alarm signals of for triggering safety
reactions or for blocking/signaling 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 using an easy-to-fit
module. The module also contains an alarm output (see Alarm
module).
Limit value signal via mechanical contacts (Limit value contact
module)
Galvanic isolated switching contacts could indicate two redundant
limits through an easy mounted module. 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.
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 similar,
and is connected to the travel detection system by an electric cable
and to the actuator by one or two pneumatic lines. Such a split design is frequently advantageous if the ambient conditions at the
fitting exceed the specified values for the positioner. The followin
g 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)
The use of linear potentiometers is recommended for very small
actuatorswith a short valve travel since, on the one hand, the space
required by the linear otentiometer is very small and, on the other,
the transmission characteristic is optimum for a small travel.
>14 mm, the magnet and the NCS are premounted on a stainless
steel frame and offer the same interface mechanically as the
positioner itself, i.e. they can be mounted using the standard
mounting kits 6DR4004-8V, -8VK and -8VL.
The installation of a EMC filter module in the positioner (controller
unit) is necessary in order to ensure a connection level with EMC
according to EN 61326/A1 and NAMUR NE21 when using external
sensors (see Ordering data for "EMC filter module")
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