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Safety Guaranteed: Pepperl+Fuchs Extends Portfolio of Safe Absolute Linear Positioning Systems up to SIL 3 and PL e


Safe Evaluation Unit (PUS)

Safe Evaluation Unit (PUS)
Pepperl+Fuchs introduces a new safe evaluation unit (PUS).

Pepperl+Fuchs combines a new safe evaluation unit with the advantages of the proven safePXV and WCS absolute positioning systems, expanding the portfolio for safe absolute positioning. The new system consisting of the safe evaluation unit (Position Unit Safe, PUS) and one safePXV/PUS or two safeWCS/PUS read heads enables safe position and speed detection up to SIL 3 and PL e. The evaluation unit processes and evaluates the redundant signals from the sensors and transmits them to a safe controller. With the expanded portfolio, Pepperl+Fuchs now offers several solutions for safe and robust position detection in a wide range of applications—even in challenging environmental conditions.

Multiple Redundancy: safePXV/PUS

The PXV absolute positioning system is based on a read head and a Data Matrix code tape. With an innovative, multicolor concept, the safePXV safe standalone variant already has multiple redundancy in itself. The multicolor Data Matrix codes on the robust code tape are made visible and read by the two-color illumination of the safePXV read head. Due to the large reading window, the safePXV read head always reads several codes at once. This makes the system very resistant to interference—even if the code tape is dirty or damaged, the sensor reads the data reliably. The safePXV's algorithm already checks the plausibility of the data in the sensor itself. In combination with the new safe evaluation unit, the evaluated data—in addition to the PROFIsafe safety protocol—is now also transmitted to the safe controller via FSoE.

Robust and Proven for Decades: WCS

Pepperl+Fuchs introduced the WCS position encoding system as early as 1989 and has continued to develop it ever since. The absolute positioning system is based on the combination of a read head in a robust housing and a code rail made of stainless steel or plastic. This makes the WCS particularly suitable for use in demanding environments and for long distances. The outdoor version defies extreme outdoor conditions thanks to the special housing of the WCS read head. In combination with the new safe evaluation unit, the proven WCS is now also available for applications that require a safety level up to SIL 3/PL e. Two safeWCS/PUS read heads are used for this purpose, which are mounted one behind the other on the code rail. To ensure separate redundant signaling, one read head is parameterized for forward movement and one for reverse movement.

Minimum Effort, Maximum Safety: Position Unit Safe

The new safe evaluation unit (PUS) acts as a safe gateway to the fieldbus: It processes the redundant signals from the safePXV/PUS and safeWCS/PUS read heads, creates a safe position value, and derives a safe speed value from it. In addition to the safe and non-safe data, it also transmits diagnostic data that is available as a basis for condition monitoring and predictive maintenance. The two positioning systems safeWCS/PUS and safePXV/PUS are remarkably easy to integrate into higher-level systems. They support the common safety protocols PROFIsafe and FSoE in order to transmit the acquired data from the sensors to a safe control system.

Being TÜV-approved with pre-certification and EC type examination certificate up to SIL 3/PL e and preconfiguration, the systems, consisting of evaluation unit and sensor technology, are also especially quick and easy to commission. Pepperl+Fuchs provides users with a tested preconfiguration for safeWCS/PUS and safePXV/PUS. Since the most frequently required application settings are already preprogrammed, the systems can be used directly in numerous use cases. At the same time, the preconfiguration facilitates device replacement. If a fault occurs, the read heads can be replaced during operation without any adjustments. This increases system availability and saves time and costs.

Pepperl+Fuchs offers several solutions for safe and robust position detection in a wide range of applications—even in challenging environmental conditions.

Highlights of Safe Absolute Linear Positioning Systems

  • Safe absolute linear positioning systems up to SIL 3/PL e
  • Exceptionally robust position detection for use in challenging environmental conditions
  • Reliable monitoring of safety-relevant applications through output of safe position and speed
  • Precise position detection over long distances—even on curved paths, inclines, slopes, interruptions in the code rail or tape, or path switches
  • Fast and easy commissioning due to pre-certification and configuration


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