A rotary encoder monitors angular differences in motion or position, aiding machines as they move and helping ensure movements match required specifications. A technologic journey that started with the first optical encoders built in the 1850s has quickly grown to become a 2 billion dollar market today. Let’s break down the different types of rotary encoders and their major applications across three different fields.  


The Main Rotary Encoder Types 

There are three different subsets of rotary encoders:

  • Optical
  • Capacitive 
  • Magnetic (on and off-axis.) 


Optical Encoders 

Optical encoders measure position by passing light through an encoder disc designed with opaque and clear tic marks. As the disc rotates, the light becomes obscured or visible to the sensor. These pulses then translate into motion data.

While these encoders can achieve high resolutions, environmental factors such as excess light, dirt, or motion can disrupt their accuracy.


Capacitive Encoders

Capacitive encoders use a rotary disc etched with a sinusoidal pattern. High-frequency signals pass through the rotating disc, and the signal modulates in a predictive way that’s transcribed into motion data.

Unlike optical encoders, capacitive encoders are not as affected by environmental factors like dirt and rain. They are also highly resistant to motion feedback. However, they do come at a very high cost and are not as accurate as optical encoders.


Magnetic Encoders

Magnetic encoders have a polarized disc. As the disc rotates, the receiver can pick up on fluctuations in the magnetic field from the polarized disc. Those fluctuations then translate into movement data. These encoders can be “on-axis,” meaning the sensor is positioned in the center of the disc, or “off-axis,” which frees up the rotary shaft for other uses. 

Magnetic encoders are resistant to motion feedback and unaffected by environmental factors like dirt, dust, and rain. However, they are not suitable for conditions where magnetic feedback is present and are also not as accurate as optical encoders.


Absolute vs. Incremental Encoders

It’s also important to understand that every encoder falls into one of two categories: absolute or incremental. Absolute encoders have specialized discs that allow them to keep track of absolute positional data even after a movement has been completed. On the other hand, incremental encoders can only track changes in motion. 

Now that we’ve reviewed the different types of encoders, let’s dive into three different applications.


Application 1: Robotics 

The field of robotics relies heavily on encoders. Creating seamless motion requires a high degree of accuracy and reliable motion feedback that’s incredibly efficient. 

As robotics become more and more autonomous, encoder technology will continue to evolve and drive those advancements.


Application 2: Medical Equipment 

Encoders also play a significant role in measuring and providing motion feedback for advanced medical equipment.

Much like robotics, accuracy is critical. Whether it’s robotic-assisted surgery or life-saving photographs from MRIs and other scans, ensuring accurate motion is essential to catching and treating diseases. 


Application 3: Assembly Machines 

Finally, rotary encoders help keep the world’s production lines flowing. In this case, encoders help achieve high output and reduce supply waste by faulty operations, saving time and money. 

And, in more dangerous assembly operations, encoders help aid the movements of dangerous equipment like laser cutters and welding technology, so that people don’t have to put their safety at risk.


Rotary Encoder Solutions for 30 Years

At Photo Solutions, we’ve been working with robotics companies, factory managers, and medical professionals to create custom rotary encoder discs for their mission-critical designs. 

We’ve got over 30 years of experience designing and building various rotary encoder discs in aluminum, glass, and mylar. Learn more about our work or connect with our team to discuss your next project.