© exida.com GmbH berthold 0408-10 r003 v1r3.doc, Apr. 12, 2007
Rainer Faller Page 15 of 18
6 Terms and Definitions
DC
S
Diagnostic Coverage of safe failures (DC
S
= O
sd
/ (O
sd
+ O
su
)
DC
D
Diagnostic Coverage of dangerous failures (DC
D
= O
dd
/ (O
dd
+ O
du
)
FIT Failure In Time (1x10
-9
failures per hour)
FMEDA Failure Mode Effect and Diagnostic Analysis
HART Highway Addressable Remote Transducer
HFT Hardware Fault Tolerance
Low demand mode Mode, where the frequency of demands for operation made on a safety-
related system is no greater than one per year and no greater than twice
the proof test frequency.
PFD
AVG
Average Probability of Failure on Demand
SFF Safe Failure Fraction summarizes the fraction of failures, which lead to a
safe state and the fraction of failures which will be detected by
diagnostic measures and lead to a defined safety action.
SIF Safety Instrumented Function
SIL Safety Integrity Level
Type B component “Complex” component (using micro controllers or programmable logic);
for details see 7.4.3.1.3 of IEC 61508-2
T[Proof] Proof Test Interval
© exida.com GmbH berthold 0408-10 r003 v1r3.doc, Apr. 12, 2007
Rainer Faller Page 16 of 18
7 Status of the document
7.1 Liability
exida prepares FMEDA reports based on methods advocated in International standards. Failure
rates are obtained from a collection of industrial databases. exida accepts no liability
whatsoever for the use of these numbers or for the correctness of the standards on which the
general calculation methods are based.
7.2 Releases
Version History: V0, R1: Initial version; Aug. 16, 2005
V0, R2: Results from fault insertion tests integrated
Comments from FMEDA reviews integrated; Oct. 10, 2006;
Safety Manual added
V1, R0: Released version
V1, R1: 4 additional EMC capacitors on 48631SP, Rev 04
V1, R3: Editorial changes, Apr. 12, 2007
Authors: Rainer Faller
Review: V0, R2: Stephan Aschenbrenner (exida), Sept. 18, 2006;
Dr. Briggmann, Mr. Silva, Berthold Technologies, Oct. 2006
V1, R3: Mr. Silva, Berthold Technologies, April 2007
Release status: Released
7.3 Release Signatures
Dipl.-Ing. (Univ.) Rainer Faller, Principal Partner
Dipl.-Ing. (Univ.) Stephan Aschenbrenner, Partner
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