Safety absolute encoder for x/y/z axes – how to choose the right model from the amg portfolio to meet sil/pl requirements?

In modern industrial automation systems, integrating Safety solutions at the component level is no longer an advantage but a necessity. If you are looking for an absolute encoder that meets SIL (Safety Integrity Level) or PL (Performance Level) requirements for X, Y, and Z axes in CNC machines, robots, or mechatronic systems, selecting the right model is crucial – both in terms of interface and safety architecture.

The AMG Automatyka portfolio includes Safety absolute encoders with CANopen Safety interfaces (TRN/TBN series), EtherCAT FSoE (TRK), and PROFINET / PROFIsafe (TRT). This allows you to match the solution to a specific control system and the SIL/PL level required for X/Y/Z axes.

What is a safety absolute encoder and why is it crucial for x/y/z axes?

A Safety absolute encoder is a position sensor that continuously and uniquely determines the position of a moving element – even after a power loss. Unlike incremental encoders, it provides a direct position code, eliminating the need for referencing during system startup. In the Safety version, both the hardware design and software comply with functional safety standards (including IEC 61508), and the encoder itself is certified for specific SIL/PL levels.

Among the technologies used are redundant measurement channels, self-diagnostics, and safe communication protocols (e.g., CANopen Safety, FSoE, PROFIsafe), which allow errors to be detected and the system to transition to a safe state.

The role of an encoder in ensuring functional safety

Moving axes in industrial machines – X, Y, and Z – must operate with high precision, but their behavior in emergency situations is equally important. A Safety absolute encoder provides the Safety controller (PLC or drive with STO/SS1 functions, etc.) with position and speed information that forms the basis for:

• safe stopping (STO, SS1, SOS),
• monitoring speed and position,
• controlling hazardous zones.

Without a reliable, certified position sensor, it is impossible to meet SIL/PL requirements at the level of the entire axis system.

Key standards: sil and pl in the context of machinery

In machine automation, two main approaches are commonly used:

• SIL (IEC 61508 / IEC 62061) – Safety Integrity Level, most commonly SIL2 or SIL3 in drives and linear axes.
• PL (EN ISO 13849-1) – Performance Level, from PL a to PL e, with PL d or PL e typically required in X/Y/Z axis systems.

Both standards aim at the same goal: achieving an acceptable, measurable level of risk. A properly selected Safety absolute encoder (with declared SIL/PL) is one of the key component contributions to achieving that level.

Step 1: determining sil and pl requirements for your application

How to determine the required sil level?

The SIL level depends on risk analysis and factors such as:

• frequency of hazard occurrence
• the operator’s ability to avoid the hazard
• potential consequences (injury, machine damage, material loss)

In CNC machines, industrial robots, or linear axis drives, SIL2 requirements are frequently encountered – this is the level for which encoders such as TRN/TBN, TRK, and TRT are certified.

How to interpret performance levels (pl)?

In the EN ISO 13849-1 standard, the PL level (from a to e) is determined based on:

• system architecture categories
• mean time to dangerous failure (MTTFd)
• diagnostic coverage (DC)
• measures preventing common cause failures (CCF)

Safety encoders available from AMG are designed to enable the construction of systems achieving **PL d**, when combined with appropriate Safety controllers and drives.

Safety requirements checklist for x, y and z axes

Before selecting a model, answer the following questions:

• What SIL/PL level results from the risk analysis of the axis?
• Does the axis operate in collaboration with humans (cobot, handling) or in a fenced zone?
• What resolution is required (precision positioning vs zone monitoring)?
• Which Safety interface is used by your controller/drive (CANopen Safety, EtherCAT FSoE, PROFINET/PROFIsafe)?
• In what environmental conditions will the encoder operate (temperature, vibration, dust, humidity)?
• Will the encoder serve a single axis or become a standard across multiple axes?

This forms the starting point for selecting a specific device from the AMG Automatyka portfolio.

Step 2: choosing the right safety encoder model from the AMG portfolio

CANopen safety: TRN/TBN – a classic solution for CAN-based axes

If CANopen Safety is the standard in your control system, the natural choice is the TBN/TRN encoder family.

Key features:

Interface: CANopen Safety SIL2 + standard CANopen

Measurement range:

• TBN – singleturn up to 65,536 steps per revolution
• TRN – mechanical multiturn (up to 4096 revolutions)

Mechanics: various diameters (Ø42, Ø53, Ø58, Ø78), standard and compact versions, available as bearing-supported versions and kit encoders.

Environment: protection ratings from IP65/IP66 up to IP68/IP69K (optional), ATEX versions available.

Typical axes:

• X/Y/Z axes in machines with existing CANopen Safety infrastructure
• applications requiring high EMC resistance, a wide range of mechanical options, and easy integration with CAN controllers

EtherCAT FSoE: TRK – compact safety encoder for high-speed axes

If your machine is based on EtherCAT and uses Functional Safety over EtherCAT (FSoE), the TRK encoder is a strong choice.

Key advantages:

• Interface: EtherCAT with FSoE safety channel, SIL2 / PL d
• Design: very compact housing (e.g., Ø38 mm versions), ideal where space around the axis is limited.
• Safety functions: safe transmission of position and speed, enabling functions such as: SLS (Safe Limited Speed), SDI (Safe Direction)

Typical axes:

• high-speed X/Y axes in pick-and-place systems, feeders, conveyors, AGV/AMR systems
• applications requiring monitoring of safe speed and direction under high dynamics

ProfiNET/PROFIsafe: TRT – safety for demanding axes and environments

For applications based on PROFINET and PROFIsafe, AMG offers the TRT encoder, designed for Safety systems in Siemens/PROFINET environments.

Key features:

• Interface: PROFINET with PROFIsafe channel, SIL2 / PL d
• Multiturn: multi-revolution position measurement (thousands of revolutions), ideal for Z axes and rotary tables.
• Environment: high protection rating (up to IP69K), resistance to vibration and harsh industrial environments.

Typical axes:

• Z axes in CNC machines, presses, and vertical drives where safe position monitoring is critical
• systems dominated by PROFINET/Siemens controllers where maintaining a single network and Safety standard is preferred

Step 3: integration, calibration and validation of sil/pl compliance

Installation and configuration of the absolute encoder

Regardless of the selected model (TRN/TBN, TRK, TRT), the integration process includes:

• selecting the mechanical version: diameter, shaft type (solid, hollow, kit encoder), mounting method
• electrical connection according to documentation – M12 connectors and proper shielding and grounding
• configuring the Safety interface: network addressing and Safe parameters (device ID, FSoE/PROFIsafe parameterization, SRDO in CANopen Safety)

Functional testing and audit documentation

After commissioning the Safety system, it is necessary to:

• verify correct position and speed readings in both the standard and Safety layers
• test safe stop and monitoring functions (STO, SS1, SLS)
• document the configuration in a validation report (part of the SIL/PL documentation required during audits)

Encoder manufacturer (TWK) and AMG provide ready-to-use safety data (PFH, DC, SFF) that can be directly used in SIL/PL calculations.

Diagnostic tools and monitoring

Safety encoders supplied by AMG provide advanced diagnostics, including:

• signaling of transmission and power errors
• reporting of internal sensor faults
• monitoring of parameters (e.g., speed, temperature, Safety status) via the standard communication channel

This makes it easier to detect trends, plan maintenance, and maintain the required safety level throughout the entire machine lifecycle.

How to choose a safety absolute encoder from the AMG portfolio?

When selecting a Safety encoder for X/Y/Z axes, consider several key points:

1. Safety level – match certification (SIL/PL) to the results of your risk analysis.

2. Safety interface:

•  CANopen Safety → TRN/TBN
• EtherCAT FSoE → TRK
• PROFINET / PROFIsafe → TRT

3. Axis operating characteristics – singleturn vs multiturn, speeds, motion dynamics.

4. Environmental conditions – required protection rating.

5. Standardization – if possible, unify the encoder family across multiple axes to simplify service and spare parts management.

AMG Automatyka offers a full range of Safety absolute encoders – from CANopen Safety (TRN/TBN), through EtherCAT FSoE encoders (TRK), to PROFINET / PROFIsafe (TRT). If you need help selecting an encoder for a specific X/Y/Z axis, the required SIL/PL level, and a Safety controller, contact the AMG technical team.