Overview
What are Encoders?
Encoders are electromechanical sensing devices that convert physical motion—rotary or linear—into electrical signals. These signals are processed by motion controllers, PLCs, or variable speed drives to determine position, speed, direction, or count. In industrial automation, encoders are critical for ensuring precision in closed-loop systems, allowing machines to verify that mechanical movements match the commands issued by the control system.
Encoders are generally categorized by their sensing technology (optical, magnetic, or capacitive) and their output type. Incremental encoders are often used for speed control and simple positioning, while absolute encoders are used for complex axes where position data must be maintained during power cycles.
Main Manufacturers
Our inventory includes heavy-duty and precision encoders from the industry's leading brands:
- Allen-Bradley: High-performance rotary encoders for the North American market, including rugged NEMA-rated models.
- Siemens: Integrated solutions for SIMOTICS motors and SINAMICS drives.
- Bosch Rexroth: High-resolution feedback systems for IndraDrive and CNC applications.
- SEW-Eurodrive: Specialized encoders integrated into gearmotors and MOVITRAC/MOVIDRIVE systems.
- ABB: Robust encoders for heavy industrial processes and large motor synchronization.
- Delta Electronics: Cost-effective, high-resolution incremental and absolute encoders for general automation.
Typical Applications
Encoders are foundational components in any application requiring motion feedback:
- CNC Machining: Providing sub-micron positioning for tool paths.
- Conveyor Systems: Synchronizing belt speeds for multi-stage sorting and packaging.
- Robotics: Tracking joint angles in 6-axis articulated arms for precise spatial movement.
- Elevators and Hoists: Monitoring car position and ensuring smooth deceleration for floor alignment.
- Automated Storage and Retrieval Systems (ASRS): Managing high-speed XY positioning in warehouse environments.
Selection Guide
When selecting an encoder for replacement or new design, consider these technical parameters:
- Resolution: For incremental encoders, this is Pulses Per Revolution (PPR). For absolute, it is measured in bits (e.g., 13-bit single-turn).
- Mechanical Interface: Determine if you need a solid shaft (requiring a coupling) or a hollow shaft (clamped directly to the motor). Standard diameters include 6mm, 10mm, and 12mm.
- Electrical Output: Match the driver circuit (TTL/RS422 for long cable runs or HTL/Push-Pull for noise immunity).
- Protocol: Ensure compatibility with the controller, whether using traditional analog signals or digital fieldbus protocols like EtherNet/IP, PROFINET, or BiSS.
- Environmental Rating: Standard encoders are IP50 or IP65; wash-down or outdoor environments may require IP67 or IP69K stainless steel housings.
1 product · Siemens
Frequently asked questions
What is the difference between incremental and absolute encoders?
An incremental encoder provides relative position data by generating pulses as the shaft moves, requiring a reference 'home' point upon startup. An absolute encoder provides unique digital codes for every position, allowing it to retain the exact shaft location even after a power loss without needing a reset cycle.
How do I choose the right replacement encoder?
Key specifications include the physical mounting (solid shaft vs. hollow shaft), the measurement type (incremental vs. absolute), the resolution (Pulses Per Revolution or bits), and the communication interface (SSI, EtherCAT, PROFINET, or HTL/TTL square wave). You must also match the voltage (typically 5VDC or 10-30VDC).
Can I swap encoder brands for my motor?
Yes, though some adjustments may be needed. For example, many Allen-Bradley 845H series encoders can be replaced by equivalent Siemens or Bosch Rexroth models if the mounting flange and electrical interface (like SSI or EnDat) are identical. However, proprietary motor-integrated encoders from SEW-Eurodrive often require exact OEM replacements to function with the drive's firmware.
When should I use a rotary vs. linear encoder?
A rotary encoder measures the rotational movement of a shaft, while a linear encoder measures movement along a path or scale. Rotary encoders are common on motors and conveyors; linear encoders are used for high-precision CNC machining and XYZ gantry stages.
Why is my encoder losing pulses?
Common causes include mechanical misalignment of the coupling, electrical noise (EMI) due to poor shielding, ingress of oil or dust damaging the optical disk, and vibration exceeding the rated G-force of the internal glass scale. High-vibration environments should use magnetic encoders instead of optical ones.