How to Choose the Right Encoder: A Complete Guide for Engineers and Integrators

CONTENTS:

  1. What Is an Encoder and Why Is It Critical?
  2. Key Parameters to Consider When Selecting an Encoder
  3. Understanding Encoder Types and Technologies
  4. Encoder Technologies: Magnetic, Optical, Capacitive
  5. Application-Based Encoder Selection
  6. Common Mistakes to Avoid When Choosing an Encoder
  7. Conclusion

Selecting an encoder is one of the critical stages in designing and configuring automation and motion control systems. The right decision determines the stability of the equipment, the accuracy of position tracking, and the speed of the system's response. In this guide, we will consider in detail how to choose the right encoder, what technical parameters to focus on, as well as what types of encoders exist and in which industries each technology is used. Thanks to this encoder selection guide, engineers and integrators will be able to make an informed decision and avoid typical mistakes.How to Choose the Right Encoder

 What Is an Encoder and Why Is It Critical?

An encoder is a device that converts mechanical motion into an electrical signal, which is then used to determine the position, speed, or direction of movement of an object. Such position feedback devices are widely used in drive control systems, electric motors, as well as industrial robots, CNC, along with conveyor lines and other automated equipment.

Depending on the configuration, encoders can provide output signals about:

  • current position (angular or linear);
  • direction of rotation or movement;
  • speed of movement of the object.

Motion control encoders play a very important role in systems where precision, synchronicity and predictability of movements are required. Their use provides continuous control, feedback and adaptation of equipment to external conditions.

 

Key Parameters to Consider When Selecting an Encoder

Before we move on to choosing a model, it is important to clearly define the requirements of your system. The main parameters to consider are listed below:

  • Resolution and accuracy. One of the most important criteria: the higher the resolution (in pulses per revolution - PPR), the more accurately the position is tracked. However, high resolution is not always necessary - for simple applications, basic values are sufficient.
  • Output signal type. Depending on the control system, you may need a digital output (TTL / HTL), an analog signal, or absolute data transmission. When choosing, be sure to check the compatibility with your controller.
  • Shaft type. There are three options: solid, through (hollow shaft) and blind shaft. They differ in the mounting method and are used depending on the design of the machine shaft.
  • Electrical interface. Modern encoders can support SSI, CANopen, EtherCAT, Profibus and other industrial interfaces. This is especially important for systems with a distributed architecture and high data exchange rates.
  • Degree of protection. For use in harsh conditions, it is necessary to consider the IP rating, resistance to shock and vibration. Some models can withstand dust, moisture, temperature changes and dirt.
  • Size and mounting method. Compact encoders are used in robotics and medical equipment, and standard ones are used in industrial automation. Different types of flanges and mounting holes allow you to choose the right solution for any task.

Understanding Encoder Types and Technologies

Now let's look at the existing types of encoders.

Incremental Encoders

Incremental encoders work by generating a series of pulses when the shaft rotates. Each pulse represents a unit of movement. They usually have three channels: A, B, and Z. Channels A and B allow you to determine the direction of movement, and Z is a zero mark for zeroing the position.

Encoders of this type are widely used due to their simplicity, availability, and high response speed. However, their main drawback is the loss of position data after power is turned off, since they do not store the absolute coordinate.

Incremental vs absolute encoders is one of the main comparisons that is worth making before choosing a device. If your system requires constant feedback, the incremental option may not be enough.

Absolute Encoders

Absolute encoders provide a unique position value at each step, which allows you to accurately restore the coordinate even after a system restart. There are single-turn and multi-turn, depending on the stroke length.

Such models are especially useful in closed-loop control systems, where it is critical not to lose position information. An encoder for motion control in precision and robotic systems almost always refers to the absolute type.

Rotary vs Linear Encoders

The difference between rotary and linear encoders is the nature of the motion they measure.

Rotary encoders record rotational motion and are installed on the shafts of motors or mechanisms. This is the most common type used in automation, drives, and CNC.

Linear encoders, in turn, record translational motion - they are used on guides, rails, linear actuators. In conditions of high accuracy and minimal tolerances, preference is given to them.

Encoder Technologies: Magnetic, Optical, Capacitive

Encoder selection directly affects the accuracy, stability of the signal, as well as sensitivity to interference and resistance to environmental conditions. There are three main types: magnetic, optical and capacitive. Each of them has its own advantages and limitations.

Magnetic encoder for motion control uses the interaction between a magnetic field and a Hall sensor or other sensing element. Such devices demonstrate good resistance to dirt, moisture, dust, and vibration. This makes them an excellent choice for use in harsh environments, such as agricultural or construction equipment. However, magnetic models are slightly inferior in resolution and stability to optical analogs.Magnetic encoder scheme

Optical encoder for automation provide high accuracy and resolution by using infrared or laser radiation passing through a specially marked disk. Such devices allow you to receive data on movement with an accuracy of up to fractions of a degree or micrometer. They are used in high-precision CNC machines, medical equipment and laboratory automation. The main limitation is sensitivity to contamination, condensation and impacts. For reliable operation, optical sensors require a clean environment and high-quality protection.

Capacitive industrial encoders are considered a relatively new technology. They work by measuring changes in the electric field between two plates when moving. Compact, energy-efficient, and less sensitive to optical and magnetic interference, such devices are used in portable electronics, compact servo drives, and lightweight robotic mechanisms. The main disadvantage is limited resolution and sensitivity to humidity. Optical encoder

Application-Based Encoder Selection

Choosing the right encoder depends on the specifics of the application. Below we will consider the most common use cases and solutions suitable for them.

For Industrial Automation

In industrial automation systems such as conveyor belts, packaging lines or sorting equipment, encoders perform the function of position and speed monitoring. The combination of reliability, ease of integration and resistance to contamination is important here. Incremental encoders with HTL output are often used in such tasks, since they are easy to connect to PLCs and frequency converters. High response speed is also appreciated, especially in high-performance lines. Magnetic rotary encoders are great for working in dusty or humid environments.encoder application

For Robotics

An encoder for robotics is responsible for precise positioning of joints, feedback during movement and control of drives. The ability to save position data even after power is turned off is especially important - this makes absolute encoders relevant, both single-turn and multi-turn. Depending on the design of the robot, both hollow shaft encoders (for compactness) and miniature linear sensors for determining the stroke can be used. In addition, it is necessary to consider the level of vibration and potential electromagnetic interference, choosing a stable and shielded model.

For CNC and Precision Motion Systems

Machines with numerical control, engraving devices and high-precision drives require encoders with high resolution and low signal noise. Optical absolute encoders, which provide feedback in real time, are especially in demand here. The encoder must have high linearity and resistance to temperature fluctuations. Compatibility with digital protocols (SSI, BiSS, EnDat) is also taken into account, which allows the device to be integrated into a common coordinate system.

For Harsh Environments

In environments such as open construction sites, agricultural machinery or marine equipment, automation sensor solutions are exposed to vibrations, dust, dirt, moisture and temperature changes. Here, mechanical and electrical reliability are more important than accuracy. Most often, magnetic incremental encoders with a high degree of housing protection (IP67 and above), reinforced bearings and a UV-resistant plastic or metal housing are used. Anti-corrosion coating and protection against voltage surges are also important.

Common Mistakes to Avoid When Choosing an Encoder

Even experienced engineers sometimes make mistakes when selecting encoders, which can lead to system failures or unnecessary costs. Here are the most common mistakes to avoid:

  1. Ignoring resolution requirements. Insufficient resolution will result in jumpy positioning and reduced accuracy, while excessive resolution will increase cost and complexity of the system. Always calculate the required value depending on the mechanics of the system and the acceptable error.Linear encoder
  2. Incorrect selection of the signal type. Using, for example, a TTL signal without support on the controller side will lead to incorrect operation. Before purchasing, make sure that the encoder interface meets the requirements of your electronics.
  3. Underestimating the operating conditions. Installing an optical encoder in a dusty environment without proper protection will quickly disable it. Likewise, a device without vibration isolation can fail under constant impact or shaking. It is necessary to carefully evaluate the real conditions.
  4. Over-redundancy. Some projects use expensive absolute encoders where more affordable incremental models would do. Or they order interfaces that will not be used. This leads to unnecessary costs without increasing efficiency.

Conclusion

Choosing an encoder requires a comprehensive approach. You should consider industrial encoder types, their resolution, signal shape, as well as dimensions, shaft type and resistance to external influences. It is equally important to understand how the device will integrate into an existing system and what tasks it will perform.

Need help choosing the right encoder? Explore our full range of incremental and absolute encoders at Eltra Trade or contact our team for expert advice!




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