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0 About This Manual
0.3 Abbreviations and symbols
26
ZB12-…, ZB32-…
11/16 MN03407004Z-DE/EN
www.eaton.com
0.3 Abbreviations and symbols
Symbols used in this manual have the following meanings:
Ex e
Type of protection “Increased Safety”
FIT
F
ailure
I
n Time
(number of dangerous failures in 10
9
hours)
HFT
H
ardware-
F
ault-
T
olerance
HM
Highest possible setting current
MTTF
d
M
ean
T
ime
T
o
D
angerous
F
ailure
NM
Lowest possible setting current
PL
P
erformance
L
evel
PTB
P
hysikalisch-
T
echnische
B
undesanstalt
(German Federal Testing Laboratory: Accredited certification authority for devices
operated in Ex e areas)
SIL
S
afety
I
ntegrity
L
evel