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Why employ SIL 3-suitable encoders?Using certified safety devices has advantages: engineering efforts for machine builders are minimized, thus reducing costs and implementation times. In addition, the safe position value no longer needs to be checked by the controller. An implementation with standard components, which are required twice, often does not cover common cause failures (CCF) either, thus forcing users to take special, cost-intensive measures and to validate process data in the controller. An implementation with standard components therefore often requires significant additional efforts.
Encoder FeaturesThe new encoders from POSITAL fulfil the requirements of IEC 61508, EN 62061 (SIL CL 3) and EN ISO 13849 (performance level e). Operated with protective extra low voltage (PELV), they are suitable for use in drive technology, lift applications, mobile machines, construction machinery and machine tools. Equipped with a CANopen interface, the safety encoders support the CANopen Safety protocol according to CiA 304 as well as standard CANopen DS-301, which allows for easy communication with other standard CANopen nodes. They perform bit-inverted safety checks. A special feature is the redundant encoder design: thanks to dual opto arrays and two gearboxes, the units ensure optimal reliability while measuring only 16 mm more than standard models.
Like all OPTOCODE encoders, the new safety models use a proven opto-electronic scanning method to measure position values. The single-turn sensor provides a resolution of 16 bit per revolution. Additionally, a maximum of 16.384 revolutions (14 bit) can be registered in multi-turn mode, thereby covering a 30 bit measuring range. The encoders provide two-channel position detection. The measured position data is routed to a CANopen safety chip with a SIL 3 certificate, where it is processed by means of two-channel evaluation algorithms. Moreover, the redundant units counter-check the results. Two CAN controllers, which take turns in transferring the bit-inverted, safe position values, ensure the CANopen connection. Optionally, the units can also be used as standard encoders. Integration into the fieldbus system is ensured by a rotary switch at the connection cap which allows users to configure node number and Baud rate (up to 1 MBaud). Models with a plug or cable connection are configured via SDO telegrams. The encoders are available as solid shaft, hollow shaft or synchronous shaft models. They provide IP65 protection on the housing side and IP64 on the shaft side (an optional sealing ensures IP66).
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