The SIPART PS2 positioner is a digital field device with a highly-integrated microcontroller.

The positioner consists of the following components:

• Enclosure and cover
• Printed circuit board with corresponding electronics with or without communication through HART 7
  or with electronics for communication in accordance with
  • PROFIBUS PA specification, IEC 61158-2; bus-supplied device, or
  • FOUNDATION Fieldbus (FF) specification, IEC 61158-2, bus-supplied device
• Position detection system
• Terminal housing with screw terminals
• Pneumatic valve manifold with piezoelectric valve precontrol

The valve manifold is located in the housing, the pneumatic connections 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 positioner is fitted to the linear or part-turn actuator using an appropriate mounting kit. The circuit board container in the casing provides slots for separately ordered boards with the following functions:

Position feedback 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, e.g. 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. An alarm output is also integrated in the module (see "Alarm Module").

Limit value signal via mechanical contacts (mechanical limit switch module)

Two limits can be signaled redundantly by switching contacts. An alarm 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 modules are easy to retrofit.

Separate mounting of position detection system and controller unit

The position 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 position 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 (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 k? resistance), e.g. for higher application temperatures or customer-specific applications

The use of potentiometers is recommended for very small linear actuators with a short valve travel since, on the one hand, the space required by the potentiometer is very small and, on the other, the transmission characteristic is optimum for a small travel.

Separate mounting of position detection system and controller unit

Non-contacting position sensor (NCS)

NCS for part-turn actuator mounted with mounting bracket (6DR4004-.N.10, left) and for linear actuator ? 14 mm (0.55 inch) mounted with actuator-specific mounting solution (6DR4004-.N.20, right)

NCS (6DR4004-.N.30) for travels > 14 mm (0.55 inch) mounted using mounting kit for NAMUR linear actuator

The NCS sensor consists of a non-contacting position sensor. 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 for up to 14 mm travel.

This results in:

• Even greater resistance to vibration and shock
• No wear of position 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 Ex d version) can be operated in a 2-wire system. The NCS (Non Contacting Sensor) consists of a potted sensor housing which must be mounted permanently and a magnet which is mounted on the spindle of linear actuators or on the shaft butt of part-turn actuators. For the version for travels >14 mm (0.55 inch), 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 an EMC filter module in the positioner (controller unit) is necessary in order to provide a process boundary when external position sensors are used and to ensure immunity to noise according to the EC Declaration of Conformity (see "Selection and Ordering Data", "EMC Filter Module").