Selecting Encoders: Incremental, Absolute, and Safety

Encoders are the eyes of your motion system. Choosing between incremental, absolute, and functional safety-certified versions determines positioning accuracy, recovery behavior, and compliance with modern safety standards.

Incremental Encoders

• Output A/B/Z pulse trains.
• Require homing sequence on startup.
• Ideal for cost-sensitive or speed-only applications.

Absolute Encoders

• Provide unique position value per shaft revolution (single-turn) or across turns (multi-turn).
• No homing required — position known instantly after power-up.
• Interface via SSI, BiSS, or EnDat protocols.

Safety Encoders

• Certified per IEC 61800-5-2 for SIL2/3 applications.
• Include redundant tracks or channels for fault detection.
• Required for safety functions like SLS, SSM, or SDI.

Environmental and Application Factors

• Magnetic types resist oil and vibration but offer less precision.
• Optical types achieve sub-micron accuracy but need clean environments.
• For vertical axes, absolute encoders prevent drift recovery errors.

Example

A press automation line upgraded to SIL2 encoders on critical axes. The result: zero unexpected restarts and compliance with ISO 13849 PL d.

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Conclusion

Encoder selection defines motion reliability. Balancing cost, resolution, and safety compliance ensures accuracy — and peace of mind.