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Single-turn vs. Multi-turn

March 29, 2022

For rotary encoders the terms single-turn and multiturn are used. The difference between the two is that with a single-turn encoder, the output codes are repeated with each revolution of the encoder shaft. There is no data indicating whether the encoder has made one or 1000 revolutions. With multiturn absolute encoders, the output is unique for each shaft position at each revolution up to a certain number of revolutions (e.g. 4096).

An additional functionality of some multiturn encoders is the ability to count the number of full revolutions even if the encoder is not powered. In order to achieve this additional functionality, a multiturn encoder requires additional hardware so that revolutions can be counted. This can be done in the following way:

  • Battery-powered: A battery keeps the counts across power cycles. It uses an energy saving electrical design to detect movement.
  • Geared: A gear train mechanically stores the number of revolutions.
  • Self-powered: These encoders use the principle of energy harvesting to generate energy from the moving shaft. This principle, introduced in 2007, uses a Wiegand Sensor to produce electricity sufficient to power the encoder and write the number of revolutions to the non-volatile memory.

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Posted in: Encoder knowledge