In today’s automation environments, accurate speed and position control is essential to keeping machines and systems running at peak performance. Whether you're moving a robotic arm, indexing a conveyor, or lifting with a hoist, precise motor feedback is what ensures everything moves exactly as intended. That’s where encoders come in, converting motion into usable data that enables smarter, more responsive control.
A Variable Frequency Drive (VFD) controls motor speed and torque, but without an encoder, it can only estimate actual performance. Encoders provide critical feedback, enabling closed-loop control. This allows the VFD to confirm what’s happening at the motor shaft and make immediate adjustments. The result: consistent speed, precise positioning, and better system repeatability.
Applications that benefit most from encoders include:
Encoders generally fall into two categories: motor-mounted and external, depending on where feedback is captured in the system.
Motor-mounted encoders attach directly to the back end of a motor and provide real-time feedback on speed, position, or both. Because they’re fixed to the motor shaft, they offer accurate, delay-free feedback—ideal when the load moves directly with the motor.
Common use cases:
Functional Benefits
Encoder Retrofitting and Dual Feedback
Not every application starts with encoder feedback. If speed or positioning needs change, retrofitting a motor encoder can offer a cost-effective upgrade.
In more complex systems, a dual encoder setup (motor + external) helps ensure both dynamic response and final load accuracy. The motor encoder handles fast feedback; the external encoder validates actual load position, which is critical in systems with slip, stretch, or compliance.
Interface Options
Motor encoders come in various formats, including TTL, HTL, sine-cosine, and digital interfaces like SEW-EURODRIVE’s MOVILINK® DDI. Make sure the encoder and VFD share compatible interfaces. Platforms like MOVI-C® support multiple standards out of the box, simplifying setup.
Motor encoders assume the load and motor move together—but belts, couplings, and gear lash can introduce slip or delay. External encoders measure motion directly at the load, ensuring true position accuracy.
Common types of external encoders:
When to use external encoders:
Top Functional Benefits:
Integration Considerations
Not all drives support dual encoders. High-performance drives like those in the SEW-EURODRIVE MOVI-C® modular automation platform do, offering multiple encoder inputs and broad protocol compatibility for seamless integration.
Choosing the right encoder comes down to what your system needs to know. Incremental encoders are ideal for speed and positioning feedback which do not need to be often referenced, while absolute encoders provide absolute position data even after power outages etc. Understanding their differences helps ensure accurate, efficient system performance.
An incremental encoder is a type of position sensor that converts rotary motion into a series of electrical pulses. As the motor shaft turns, the encoder generates evenly spaced pulses, often called “increments”, that the control system uses to calculate speed, direction, and relative position. They're ideal for speed-based applications due to their simplicity and cost-effectiveness.
Common interface types include:
Resolution is measured in increments per revolution (IPR), with higher IPR delivering more accurate speed control.
An absolute encoder is a type of position sensor that provides an absolute digital value for each shaft position, so it always knows the exact position, even after a power cycle. Instead of pulses, absolute encoders transmit a unique digital value for each shaft position. Upon startup, the system immediately determines the shaft position, eliminating the need for homing or referencing routines.
Common interfaces include:
To properly integrate an encoder, engineers must verify:
|
Application |
Recommended Encoder Type |
|
Conveyor with possible slip |
External (laser or barcode) |
|
Direct-drive robot arm |
Motor-mounted absolute |
|
High-speed labeling |
Motor-mounted incremental |
|
Hoist with long vertical travel |
Motor and external encoder (external) |
While not technically encoders, resolvers serve similar purposes. These analog devices are highly durable and cost-effective, often used in servo applications where environmental ruggedness and basic position data suffice. They’re well-suited for harsh or high-shock environments, though they lack the high resolution of digital encoders. Resolvers are commonly used in servo motors.
SEW-EURODRIVE uses a consistent four-character code to identify encoders:
This structure makes it easy to identify and match components during design or troubleshooting.
Encoders are key to achieving precise, repeatable motion in modern automation. Whether you’re controlling speed, position, or both, understanding the differences between encoder types and how they integrate with your drive platform helps ensure your system performs at its best.
SEW-EURODRIVE’s encoder-enabled motors and MOVI-C® drives offer broad compatibility, simplified wiring, and proven reliability. But regardless of the brand, applying encoder technology thoughtfully can elevate your automation system from functional to exceptional.
Learn More about SEW-EURODRIVE’s Encoder Systems: https://www.seweurodrive.com/products/motors/accessories-and-options/encoders/encoders.html