Encoders 007 - Encoders: Mechanical Configurations

US Digital Product Family

Encoders 007 - Encoders: Mechanical Configurations

We will continue in this post going through the various classification of encoders which were identified in my earlier post.

Mechanical Configurations

Mechanical configurations include differences based on whether the encoder comes with a shaft or will be installed onto an existing shaft. There are also different configurations based on the size of the motor, the required IP rating, and other environmental conditions.

Mechanical configurations

Motor feedback encoders may contain their own bearings, or they may use an existing bearing set such as that found on the tail shaft of a servo motor. The best configuration option to use is a function of the stability of the shaft/bearings to which the encoder is attached. Feedback encoders with bearings are typically used when the application shaft has a significant amount of axial or radial run out (eccentricity or vibration). The use of a shafted encoder with a motor will require some sort of flexible member, either a flexible shaft coupling or flexible body mount, to allow mechanical compliance with the application shaft operating irregularities.

Kit Encoder example

Modular encoders, also referred to as encoder kits, don’t contain their own internal shaft. They are assembled from components supplied by the encoder manufacturer and are designed to be attached to the tail shaft and end bell of the motor. These encoders rely on a mechanically stable motor shaft, as the shaft is responsible for holding the encoder’s internal rotating code wheel in a precise location relative to the encoder’s sensing module. For these applications, motor manufacturers put a considerable amount of effort in designing high-performance motors with very stable shaft/bearing assemblies. Because the modular design does not add the expense of the extra set of bearings that a motor feedback encoder does, modular encoders offer one of the most cost effective feedback solutions.

Modular encoders

When using a kit style encoder, another mechanical consideration is the size of the motor. Most encoder manufacturers supply a motor/encoder compatibility chart based on the motor size. It is recommended to use such a chart, like the one below, to help identify the appropriate encoder model.

Spec table sample
IP65 Rated encoder

Another mechanical configuration relates to environmental conditions. If the encoder will be installed in an environment that is subject to excessive dust and/or moisture, encoders are available with various IP ratings to meet those requirements. Magnetic and capacitive encoders would also be a potential candidate to meet some environmental concerns.

Modular encoders

Finally, there are many applications of encoders where they are inherently protected from physical contact. However, other encoders are located where they might be contacted by a person or object, therefore, requiring more physical protection. The above housing is machined from solid aluminum to provide the kind of protection needed in such an application.


If you are afraid of spiders, you might want to skip our next post which is scheduled for May 28th.

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