Choosing the right encoder for your application

Selecting the best encoder for your application is crucial for optimizing performance, reducing operational costs, and extending the lifespan of your machine tools. The right encoder not only enhances overall system reliability but also plays a key role in reducing total cost of ownership (TCO). This article explores the most important considerations when choosing an encoder, offering guidance on how to make the best choice to support your specific needs.

Why choosing the right encoder is important

In any automation or motion-control application, encoders provide the feedback required to monitor motion, positioning, and speed accurately. It is also important to ensure that the encoder will operate across a machine’s lifetime without being easily interrupted from factors such as misalignment or contamination. Choosing the correct encoder provides numerous benefits including:

Optimize machine performance

Encoders come in all kinds of sizes and performance levels so selecting the proper encoder ensures you’re not overpaying and meeting your performance requirements. Understanding the differences between incremental vs. absolute, rotary vs. angular, and what your market requires will go a long way towards making an optimal selection and getting the best return on investment from a product.

Reduce the likelihood of common failures

Selecting an encoder robust enough for your environment and application helps prevent system malfunctions and costly downtimes. When encoders fail or perform inadequately, machine downtime can increase, leading to production delays. Reliable encoders can decrease interruptions in manufacturing processes by preventing breakdowns and minimizing maintenance requirements. Technologies like predictive maintenance, advanced tool breakage detection, and digital twins contribute to a streamlined approach to TCO reduction by minimizing waste and preventing unnecessary maintenance.

Critical factors in selecting the best encoder

Choosing the right encoder goes beyond simply meeting technical specifications; it involves a detailed understanding of the application and how different encoder features contribute to system performance. Here are critical factors to consider:

Understanding different types of encoders

There are three primary types of encoders: linear, rotary, and angle. Let’s take a look at the difference between them.

• Linear Encoders measure straight-line motion, using sensors that attach to moving parts along guideways. They are often employed in applications requiring precise linear feedback, such as in CNC machining and motion stages.
• Rotary Encoders measure rotational movement, often in systems where speed control is essential, like servo motors. Key attributes for rotary encoders include positioning accuracy, speed stability, and bandwidth, as these impact motor performance significantly.
• Angle Encoders are also rotary but provide much higher precision at lower rotational speeds, ideal for applications that demand extreme accuracy, such as semiconductor manufacturing.

Absolute vs. incremental encoders

One of the first considerations in choosing the right encoder is whether your application requires an absolute or incremental encoder or distance coded encoder. Choosing between these types depends on whether your application needs consistent positioning on startup or is able to make the required movements for homing across a reference mark. Here is a quick overview of each:

• Incremental encoders measure movement relative to a start position, with each movement marked by identical, evenly spaced line across the scale. They are often more affordable and output a simpler position signal but requires the machine to move past a “reference mark” in order to establish it’s position. They are ideal for applications focused primarily on speed control.
• Absolute encoders, in contrast, provide continuous position data with unique codes for each, maintaining it’s exact location without any reference mark, even after power loss. Absolute encoders are suited to high-precision applications in which you don’t want movement during startup, such as with large scale machinery.
• Distance coded lies between incremental and absolute by using evenly space lines like incremental but has uniquely spaced reference marks across its entire length which provides absolute positions with smaller startup motions.

Environment and installation considerations

The environment in which the encoder will operate plays a significant role in its selection:

Sealed vs. exposed encoders

Sealed encoders are encased within an aluminum extrusion designed to protect delicate components from contaminants like dust, coolant, or debris, making them ideal for industrial settings such as Machine Tool. Exposed encoders, on the other hand, have no such protection but are able to reach much higher levels of position acuracy, making them better suited for high performance, low-contamination environments such as semiconductor manufacturing.

Operating conditions and mounting

Requirements such as temperature, humidity, and potential vibration need to be evaluated as these factors will influence the encoder’s performance and longevity. All products have an IP rating which states what types of contaminants it can withstand without effecting performance. Common questions to consider include: Will the encoder be exposed to contaminants? What kind of surface will the encoder be mounted to? What are the temperatures of the environment?

Application-specific needs

Different applications require unique encoder specifications:

• Medical and Semiconductor Industries: In medical imaging or semiconductor fabrication, precise measurement is critical. Encoders with high resolutions and fine graduations, such as HEIDENHAIN’s optical encoders, are typically used in these applications. These commonly use exposed linear encoders.
• Robotics: For applications involving robotic arms or mobile robotics, encoders must offer compact profiles and accurate speed and positioning feedback. These commonly use rotary encoders.
• Machine Tool: Within metal cutting, the encoder operates alongside liquids and is exposed to strong vibrations so the encoders much be able to withstand harsh environments. These commonly use sealed encoders.

Feedback type and interface

Feedback types and interfaces are essential for communication between the encoder and control systems. Encoders support various interface options to suit specific applications:

Incremental interfaces use pulse-based feedback and can be in the form of an Analog (1 Volt Peak to Peak) or Digital (transistor-transistor logic) signal. These types of signal are near universally read across many controller types.

Absolute interfaces take the form of bits and bytes, offering a lot more position detail than incremental. These can take the form as either a proprietary interface (such as HEIDENHAIN’s EnDat Platform) or an open interface which provide flexibility for multi-brand hardware compatibility. Before selecting an absolute interface, it’s critical to make sure the controller can read the signal.

Ensuring compatibility with control systems is essential to optimize encoder performance. For instance, high-speed applications may require interfaces with higher bandwidth to maintain speed stability. To prevent performance issues, check for compatibility with the control system and assess how the encoder will integrate within your system’s feedback loop.

Single-turn vs. multi-turn encoders

For rotary feedback specifically, you may need either a single-turn or multi-turn encoder:

• Single-turn encoders: These track position within a single 360-degree rotation and are ideal for applications that don’t require tracking of total revolutions, like antennas and pivoting points.
• Multi-turn encoders: These track revolutions beyond 360 degrees, making them suitable for applications like cranes, robotic joints, and wind turbine pitch control. Multi-turn encoders are available with battery backups, gears, or magnetic pulses to retain position data even during power cycles.

Invest in the right encoder

Choosing the right encoder for your application is essential for ensuring reliable feedback, reducing costs, and optimizing performance over the machine’s lifecycle. The decision-making process involves understanding the environmental, application-specific, and technical requirements for an encoder.

As you evaluate options, HEIDENHAIN’s wide range of encoder technologies—including advanced predictive maintenance tools, digital twins, and automation-friendly encoders—offer comprehensive solutions for reducing TCO while achieving higher efficiency. Investing in the right encoder is an investment in long-term operational success, and with innovations like EnDat 3 simplifying interface requirements, HEIDENHAIN continues to support businesses in creating durable, cost-effective solutions.

For more guidance on selecting the right encoder, or to explore HEIDENHAIN’s offerings, reach out to our team to start a consultation tailored to your unique requirements.