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V01.00 | 2020/04
5.3
FMEDA results
The following safety characteristic are results of FMEDA.
Digital output
λ
SD
λ
SU
λ
DD
λ
DU
λ
AU
No effect
DC [λ
DD
/λ
D
] SFF
IMX12-FI01-1SF-1R 0 FIT
196.5 FIT
249.5 FIT
38 FIT
0 FIT
409.4 FIT
86,78 %
92.15 %
IM12-FI01-1SF-1R
0 FIT
196.5 FIT
249.5 FIT
38 FIT
0 FIT
409.4 FIT
86,78 %
92.15 %
The stated Safe Failure Fraction (SFF) is for reference only. The complete subsystem will need
to be evaluated to determine the overall SFF. The failure rates used in this analysis are the basic
failure rates from the Siemens standard SN 29500 based on the average ambient temperature
of components of 40 °C.
“No effect” is a failure mode of a component that plays part in implementing the safety func-
tion but is neither a safe nor a dangerous failure. According to IEC 62061, it would be possible
to classify the “No effect” failures as “Safe Undetected” failures. Not doing so represents the
worst-case.
5.4
Examples for using the results
5.4.1
Probability of dangerous failure per hour (High Demand Mode)
The sum of the diagnostic test interval and the time to achieve the specified safe/alarm state is
less than 1 s. The ratio of the diagnostic test rate to the demand rate shall equal or exceed 100.
Digital Output
PFH
IMX12-FI01-1SF-1R
39.99E-09 1/h
IM12-FI01-1SF-1R
39.99E-09 1/h