OPTISWITCH 3300 C with contacless electronic switch - Fagerberg

Functional safetyLow demand modeHigh demand model The communication via the IIC bus interface is only usedfor default scaling and for service purposes.l The repair time (exchange of the measuring system) after afail-safe error is eight hours (MTTR = 8 h)l In the mode with the lowest demand rate, the reaction timeof a connected control and processing unit to dangerousdetectable errors is max. 1 hour.If the demand rate is only once a year, then the measuringsystem can be used as safety-relevant subsystem in "lowdemand mode" (IEC 61508-4, 3.5.12).If the ratio of the internal diagnostics test rate of the measuringsystem to the demand rate exceeds the value 100, themeasuring system can be treated in the way it is executing asafety function in the mode with low demand rate (IEC 61508-2,7.4.3.2.5).Corresponding characteristics is the value PFD avg (averageProbability of dangerous Failure on Demand). It is dependenton the test interval T Proof between the function tests of theprotective function.For number values see paragraph "Safety-technical characteristics".If the "low demand rate" does not apply, the measuring systemas safety-relevant part system in "high demand mode" shouldbe used (IEC 61508-4, 3.5.12).The fault tolerance time of the complete system must be higherthan the sum of the reaction times or the diagnostics testperiods of all components in the safety chain.Corresponding characteristics is the value PFH (failure rate).For number values see paragraph "Safety-technical characteristics".Safe condition and fault descriptionThe safe condition of the measuring system is the switched offstatus (quiescent current principle):l VB60C (contactless electronic switch) -switch openA fail-safe failure (safe failure) exists if the measuring systemchanges to the defined safe condition without demand of theprocess.If the internal diagnosis system recognises a failure, the safecondition is taken up.30 OPTISWITCH 3300 C - with contactless electronic switch29960-EN-060112