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MTTFd stands for mean time to dangerous failure. Determination of the MTTFd according to EN ISO 13849-1, Annex C.5: MTTFd = 2 × MTTF (typical) MTTFd = (2 × MTTF) / 10 (worst case) Classification according to EN ISO 13849-1:
Note! • Standard sensors from wenglor sensoric are not safety components in accordance with machinery directive 2006/42/EC. • wenglor sensoric recommends the use of safety products which have been specially developed and certified for this application. Warning! • Standard components are not suitable for personal safety tasks. • Standard optical sensors may not be used for detecting persons (in addition to MTTFd, numerous other criteria and measures must be observed in order to implement safety applications). wenglor sensoric GmbH determines MTTFd values for standard sensors based on the following: • Parts count process (DIN EN ISO 13849-1:2008, appendix D.1) • Failure rates for components (Siemens standard SN 29500) or manufacturer’s specifications for special components (e.g. ASIC) • Ambient conditions: Ta = 40 °C, Uop = 24 V DC • A safety factor of 10 (see also EN ISO 13849-1, appendix C.5.1) is not used for the specified data sheet value because correct use of the data sources can be assured. In addition to the MTTFd value designated in the data sheet, the following characteristic values apply to standard sensors: • DC = 0%. Standard products do not have any diagnostic coverage. • TM = 11.42 a (photoelectronic sensors and ultrasonic sensors) • TM = 20 a (inductive sensors and other sensors) • This data is valid insofar as not otherwise stipulated in the data sheet or operating instructions.
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