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V01.00 | 2020/04
IM12-FI01-1SF-1R
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Appendix: Terms and Abbreviations
DC
Diagnostic Coverage
FIT
1 FIT is 1 failure per E09 hours
FMEDA
Failure Modes, Effects and Diagnostic Analysis
HFT
Hardware failure tolerance
λ
AU
Undetected Annunciation failure rate (per hour)
Annunciation failures do not directly impact safety but impact the ability to detect a future
fault (such as a fault in diagnostic circuit).
λ
DD
Detected dangerous failure rate (per hour)
λ
DU
Undetected dangerous failure rate (per hour)
λ
SD
Detected safe failure rate (per hour)
λ
SU
Undetected safe failure rate (per hour)
MTTR
Mean time to restoration (hour)
PFD
avg
Average probability of dangerous failure on demand
PFH
Probability of dangerous failure per hour
SFF
Safe Failure Fraction
SIL
Safety Integrity Level
T1
Proof test interval (hour)
Type A
“Non-complex” element (all failure modes are well defined); for details see 7.4.4.1.2 of
IEC 61508-2
Type B
“Complex” element (using micro controllers or programmable logic); for details see 7.4.4.1.3
of IEC 61508-2
GN/RD
Pwr/Err
16 –
15 +
YE/RD
E1
YE
SUD
YE/RD
A1D
14 –
13 +
12
11
10
ON
1 2 3 4 5
NC
X1X2 X3 X4
+
X5
–
Common
Alarm
Output
10…30 VDC
SUD
only
0…3 VDC /
10…30 VDC
SUD
only
NAMUR
BN
BU
7 +
8 –
NAMUR
BN
BU
no line
monitoring
5 +
6 –
BU
BN
3
2 –
PNP/
NPN
0: 0…3 VDC
1: 5…30 VDC
BK
1 +
E1
E2
E3
A1D