Charlotte Stonestreet
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TR-Electronic presents SIL3-/PLe-Certified absolute rotary encoders – now available on ProfiNET
08 August 2013
Functional safety must be taken into account in the design of drive functions in machines and systems (SIL2/SIL3 and PLd/PLe).
Drive controllers with an integrated safety function can fulfil this task reliably as long as the position feedback of the drive is adequate. However, specific processes or risk assessments can require that the real position is not measured at the drive, but at another point in the system.
Absolute rotary encoders CDH75 and CDV75 from TR-Electronic with hollow or solid shaft can be integrated at almost any point of the power train. They measure position and speed with diverse redundancy and are certified for SIL3/PLe applications. The measured values are evaluated directly in the device and transmitted via PROFIBUS/PROFIsafe or PROFINET/PROFIsafe. Safe position and speed values are therefore available throughout the control chain. Separate safety modules are needless. If the CD_75 absolute rotary encoder is used directly in the drive, square wave or sine/cosine signals are available as controller feedback signals.
The high transmission speed of PROFINET allows position control can also be implemented without compromising on speed. Position and speed information is available in the secure bus protocol for safety tasks. As the same information is also transmitted in the unsecured protocol part and the safety checks are omitted, the values here are processed significantly faster - with positive effects on the control technology. An incremental signal fulfills local control tasks such as e.g. feedback to converters. The CD_75 safety encoder therefore enables safe position and speed feedback without additional components.