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Rotary Encoders for Functional Safety

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Functional Safety Encoder Models | SIL and PL Standards | SISTEMA | Functional Safety White Paper

The most comprehensive line of functional safety encoders up to SIL3/PLe

The goal of functional safety is to minimize or eliminate risk that can occur during normal or weakened operations of machines or industrial plants. To meet the market demands for functional safety, BEI Sensors has developed a unique range of functionally safe incremental encoders to meet the most diverse industrial applications.  

This extensive range of incremental encoders can be used in the highest industrial safety related applications up to SIL3/PLe, Cat.4. Safety applications with BEI Sensors products are as simple to implement as any other standard industrial installation.

Safety encoders exclusively featuring digital and sine/cosine analog electronic output options

The BEI Sensors functional safety encoder range is offered with a standard Sine/Cosine analog electronic output or an industry-first for safety encoders; digital (TTL or HTL) electronic output. In addition, the range provides a number of unique features:

  • Wide selection of sizes and package styles: 58 mm and 90 mm OD, shafted and through shaft up to 30 mm
  • Backward compatibility with non-safety rated encoders: Allows for existing installations to be easily upgraded
  • Stainless steel housings: Withstands harsh environments, including AIS316 for food and beverage
  • Ingress protection up to IP69K: For reliability in all types of industrial environments

SIL and PL Standards

Any automated system is likely to present a risk to persons, property or the environment. It is in this context that various security measures have been taken. Safety standards were created in this way to minimize risk.

Framed by these standards, operational safety allows, after risk analysis, an assurance of adequate protection. The hazards are anticipated during the design phase of the systems and are treated before they occur. These standards are evolving to increase the level of security and are applicable since 2012.

Safety Integrity Level (SIL) and Performance Level (PL) are defined as a measurement of the effectiveness of safety systems based on the probability of tolerable incidents that can occur within a number of processing demands. The scope of the standards are as follows:

  • IEC/EN 62061 (2013): This standard defines requirements and gives recommendations for the design, integration and validation of safety-related electrical, electronic and programmable electronic control systems for machinery. It does not define requirements for the performance of non-electronic safety-related control elements for machinery. EN 62061 represents a sector-specific standard under IEC 61508. The performance of a safety function is described by the term Safety Integrity Level (SIL).
  • EN ISO 13849-1 (2009): "Safety of machinery, Safety-related parts of control systems, Part 1: General principles for design" . This standard follows a similar process as EN 62061 with SIL but defining a Performance Level "PL". This standard may be applied to safety-related parts of control systems and all types of machinery, regardless of the type of technology and energy used.
(Probability of Failure on Demand)
(Probability of failures per hour)
Safety Integrity Level (SIL)
EN 61508
EN 62061
Performance Level (PL) EN ISO 13849-1
10 -2 < PFD < 10 -1 10 -6 < PFH < 10 -5 SIL 1 b, c
10 -3 < PFD < 10 -2 10 -7 < PFH < 10 -6 SIL 2 d
10 -4 < PFD < 10 -3 10 -8 < PFH < 10 -7 SIL 3 e


SISTEMA (Safety Integrity Software Tool for the Evaluation of Machine Applications) provides users full support in the evaluation of safety devices on machines as part of EN ISO 13849-1.

SISTEMA provides two important functions:
1. It assists users in defining the performance level (PL) required for a safety device.
2. It allows users to model the structure of the safety components and verifies the adequacy of the required PL and PL obtained by calculation, based on the data security of the components used in the loop.

Download the SISTEMA Software
Download the BEI Sensors SISTEMA Library

Functional Safety White Paper

This BEI Sensors White Paper helps engineers and systems integrators understand what the new “Machinery Safetyâ  regulation means to their company. It addresses the challenge of specifying encoders for speed monitoring in safety applications according the new EN ISO 13 849-1.

The BEI Sensors Functional Safety White Paper covers:
1. The scope of the new Standards EN ISO 13849-1 and IEC/EN 62061.
2. The basics of a safety procedure approach.
3. The design of the Motion Control architecture.
4. The most common “safetyâ  architectures in speed monitoring.
5. An example of a “safety encoderâ  implementation.
6. Solution with safety integrated devices.
7. Advantages of a comprehensive digital safety encoder range for speed monitoring.

Download the BEI Sensors Functional Safety White Paper

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