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Absolute Encoders are lengths or angle gauges which are used as way gauges at machine tools, in the handling and automation engineering and at measuring and test equipments.
Operation
Absolute Encoders distribute the layer information as a digital numerical value. This value is unique for every position in the whole measuring range, therefore no homing or reference traverse is required.
The transmission of the absolute values from the encoder to the control or to the servo amplifier is usually serial transmission. Special protocols are used, e.g.
Due to the serial communication other data still can be transmitted in addition to the current position value. This can be current temperature values of the encoder or the electrical data of the servomotor were the encoder is built-in (so-called electronic label).
Besides the serial transmission, however, more and more absolute encoders are available with different bus systems. The most important bus systems for data transmission of absolute single- and multi- turn information are::
- Profibus - Interface
- CAN- / CANopen - Bus - Interface (CAN in Automation)
- Devicenet - Interface
- AS - Interface
- several Ethernet protocols (e.g. Profinet, EtherCat, Powerlink)
Differentiation Singleturn / Multiturn
Rotary encoders differentiates to those, that can deliver information within one turn and restart with zero again for the next turn (Singleturn Encoders) and those, that can deliver information for several turns (Multiturn Encoders). Optical multiturn encoders contain several discs with code lines, that are coupled by a gearing.
Sampling methods
Furthermore you differentiate between optical (usually high-resolution) and magnetic rotary encoders (usually more robustly). Latest developments however slowly lift this distinction. So there are optical encoders with SIL certification or high-resolution magnetic encoders based on Nonius, for example.
Functional Safety - Motor Feedback
The Safety HIPERFACE encoders SKS36S/SKM36S (datasheet) are SIL2/PLd/CAT.3 certified feedback systems available for AKM Motors. Due to their high electircal and mechanical reliability, as well as their high immunity to electromagnetic and electrostatic interference (EMC), these motor feedback systems are well suited for applications in functional chains of safety oriented machine functions.
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