Safety rated SIL3 incremental rotary encoder
11 March 2009
Pepperl+Fuchs has introduced a low cost, safety rated incremental rotary encoder for drive applications that offers easy integration as well as a simple interface, which is operable without additional wiring, interface cards or safety modules. The use of existing standard components, functions and accepted communication paths are the key to the new design.
Current techniquesemployed in encoders with safety ratings achieve the required fail safe functionality in one of two ways: redundancy (two encoders) or by using a separate external monitoring unit. Both methods result in increased cost and complexity.
Pepperl+Fuchs' encoder has internal self checking compliant to SIL3 with an incremental output based on a standard Sine/Cosine interface, so the device can detect and safely communicate internal malfunctions. This enables machines and control systems to revert to a safe condition (e.g. safe stop, safe reduced speed). The new approach allows encoders to be used with existing communication paths between sensor components and plant control systems, thus permitting their application in plants with high safety categories up to SIL3 (in accordance with IEC 61508), Performance Level e according to ISO 13849, Safety Category 4 according to EN 954-1 and electrical drives according to IEC 61800-5-2.
Utilising a simple but effective method of communicating an unsafe condition to the drive by means of a simulated lead break, the RVS58S is a SIL3 safety related encoder according to IEC 61508-1.
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