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Valve Positioner Control and Monitoring with Only One Device


The First 2-Channel Isolated Barrier for Analog Signals

KCD2-SCS* interface module
KCD2-SCS* 2-channel interface module for analog signals

Pepperl+Fuchs has expanded its portfolio of K-System isolated barriers for DIN rail mounting (power rail) with the KCD2-SCS* interface module. As the first 2-channel AI/AO intrinsic safety barrier with dual function, the module can be configured individually for analog input or analog output control signals. With a compact 12.5 mm housing and a packing density of 6 mm/channel, the new module enables space-saving integration in the control cabinet. These interface modules are HART-compatible and can be used both as SMART transmitter power supplies for two-wire transmitters and as SMART current drivers for valve positioners. The module can be operated on the control side in both current sink and current source mode, with the switchover being carried out using dip switches on the front of the module. This considerably extends compatibility with a wide range of control systems.

Compact Design, Configurable Channels

A completely new feature for modules of this type is that each channel is configurable to allow positioner control on one channel (AO), and position monitoring (AI) on the second channel. Positioners ensure that the actuator is brought into a position specified by the control system. They are often equipped with analog position indicators whose feedback confirms that the position specification has been performed. These can be, for example, stroke or rotation angles, which are typically provided as 4–20 mA signals and reported back to the control system. Previously, a separate isolator module was required for the input and output signal. With the new module now available, these two functions can be used in one device for the first time. If the modules are no longer required for their original signal journey when changes are made to the system, they can continue to be used elsewhere in the system thanks to their configurability. This optimizes warehousing and ensures investment security.

The KCD2-SCS* is an intrinsic safety barrier that can be used for hazardous area applications (approved to ATEX, IECEx, and UL). A version for non-Ex signal conditioning in safe area applications is also available. For each version, there is an option of screw terminals or spring terminals with push-in connection technology. The modules are also certified up to SIL 2 (SC 3) in accordance with IEC/EN 61508 and are therefore suitable for safety applications up to SIL 2, and even up to SIL 3 when used redundantly.

Common applications for the KCD2-SCS* modules in the process industry include process control applications that have both analog input and analog output control loops, safety systems (SIS and ESD) that require SIL 2- or SIL 3-rated intrinsic safety barriers, as well as control loops located in hazardous areas. 

Convenient Installation on a Power Rail

The KCD2-SCS* devices are part of the K-System, which comprises a total of more than 200 isolated barriers and 150 signal isolators. The modules are mounted on a universal power rail. The devices are also supplied with power via this mounting rail profile with insert. 


Highlights of the KCD2-SCS* Modules

  • Universal 2-channel devices for analog input and output signals
  • Each channel can be configured individually as input or output
  • Functions: Transmitter power supply for 2-wire transmitters, current driver for positioners
  • Current sink and source on control side for analog input signals
  • Ex certifications: ATEX, IECEx, UL
  • Functional safety: SIL 2 (SC 3) acc. to IEC61508 ed2 (TÜV Rheinland)
  • Ambient temperature: -40 °C … +70 °C (-40 °F … +158 °F)
  • HART-transparent


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