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Choosing the correct encoder or resolver for your application may seem tedious, but is an important decision that needs to be carefully examined before these devices are going to be used in your plant. Encoders and resolvers often are used to sense motor shaft speed in machines and robots. Resolvers have been around longer, but encoders are more widely used in modern designs because of higher accuracy and superior digital communication interfaces.
Incremental rotary encoders work on either of three technologies: optical, magnetic or capacitive. Each technology has its drawbacks and advantages, and the right choice typically is determined by the application.
“Optical encoders can be found in office applications such as copiers, and in industrial applications such as automated guided vehicles,” says Cory Mahn, senior specials engineer at Dynapar “Magnetic encoders typically are needed in harsh conditions where optical encoders could show significant performance decrease. These applications can be overhead cranes, paper mills and steel mills.”
The vulnerable component in optical encoders is the glass disk, and various designs are available to provide protection. “Our Safety-Lock bearing design incorporates two mechanically interlocked bearings that have the maximum possible distance between them,” says Tony Udelhoven, sensors division director at Turck “This design helps protect the internal optical disk system from shock and vibration that would damage traditionally designed encoder bearings.”
Some applications are too rugged for optical encoders, and others have inherent strong magnetic fields that preclude use of magnetic encoders. “Our capacitive encoders are designed and built to meet the challenges of difficult applications as they don’t have bearings or optics, and are well-suited for direct-drive applications,” notes Joanna Suresh, product manager for motor feedback and absolute encoders at Sick.
Bearing design is critical for optical encoders because the bearings are subject to contact and wear. Magnetic encoders eliminate bearings from their design, and can also offer higher performance. No matter the type of encoder selected for a particular application, it requires an interface to other components in the automation system. As with many automation components, digital interfaces provide high-speed two-way communications, enabling high-resolution outputs and diagnostics. Although resolvers are not as widely used as encoders, they can be a good fit in certain applications.
If you are not certain of which product you should use, contact Precision Electric. You can reach us by email or telephone. Send the specifications for your application to me at the email address shown below. If you have a resolver or encoder that you would like quoted for either repair or replacement, let me know.
Ryan Chamberlin
Inside Sales, Customer Support
[email protected]
Call Toll Free: 1.877.625.2402
Sources:
http://www.sickusa.com
www.turck.us
www.dynapar.com
http://www.controldesign.com/articles/2011/EncoderResolver1101.html
