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The available models can be supplied in Singleturn or Multiturn version.

The encoders of the DeviceNet series are absolute rotary shaft encoders with an interface to connect to field bus systems according to the DeviceNet standard.
The encoders belonging to this family can be supplied in singleturn or multiturn version.
The multiturn encoders have a mechanic gear train which transmits the movement of its master disc to a series of slave discs for shaft revolution counting.
An electronic circuit cancels any mechanic backlash of the gear train, thus yielding a detection's.
They are mechanically strong and properly engineered in their electronics, optical and mechanic parts, being thus able to withstand heavy duty conditions. 
These encoders have a very good quality/price ratio.