Pepperl+Fuchs Blog

The Differences Between Absolute and Incremental Rotary Encoders

Posted by Patricia Stafford on Thu, Jul 30, 2015

What are the differences between absolute and incremental rotary encoders? Which one do I use when? These questions come up all the time. Our customers want to know.

Rotary encoders in general connect to a shaft and output pulses as the shaft rotates. You can determine the speed of an object based on how many pulses there are per revolution. The number of pulses that make up one full turn of the shaft determines the resolution. Incremental encoders have a resolution of up to 50,000 pulses per revolution (ppr) while absolute encoders have a resolution of up to 16 bits or 65,536 ppr.

You can also monitor distance using incremental rotary encoders by keeping track of the output pulse count, which represents total revolutions of the encoder shaft.

Advantages of incremental rotary encoders

The following video lets you see an incremental rotary encoder in action. It shows how bottling is done in the packaging industry.



Incremental Rotary Encoder Advantages

  • Good for simple pulse counting or frequency monitoring applications
  • Good for speed, direction, and position monitoring
  • More cost effective than an absolute encoder
  • Less complex than an absolute encoder

Absolute encoders go a step further by letting you determine the exact position of a machine, and storing that information.

Advantages of absolute rotary encoders

Absolute Rotary Encoder Advantages

  • Remembers an object’s position after a power outage
  • Continuous position monitoring
  • Speed, scaling, preset, fieldbus functions

What can you do with rotary encoders? Which industries are they used in?

Both kinds of rotary encoders, absolute and incremental, are used by the same industries, including:

  • Automotive
  • Print & Paper Industry
  • Material Handling
  • Machine & Plant Engineering
  • Doors, Gates, & Elevators
  • Packaging Industry
  • Food & Beverage
  • Mobile Equipment
  • Renewable Energy
  • Oil & Gas
  • Chemical

So which type of encoder should you choose? It all boils down to customer preference and application requirements.  For a customer who wants to use a certain type of protocol, such as PROFINET, Ethernet, or J1939, or who wants to keep track of the exact numerical value at which the encoder stopped during a power outage, the right choice would be an absolute encoder. For a customer who is conscious of keeping costs to a minimum and who is okay with using a homing sequence to find and set the starting point of an encoder to zero after a power outage, the right choice would be an incremental encoder.

In the end, the best choice is the one that works for you.

Questions about Rotary Encoders?  Get the Quick Select Product Guide


Topics: Rotary Encoders

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