12 Technical data
12.11 STO [X3]
Characteristic values
Characteristic Value
Safety level Category 4 and performance level
e or SIL3/SIL CL3.
PFH (probability of dangerous failure per hour) 3 x 10
–11
PFD (probability of dangerous failure on demand) 5 x 10
-6
DCavg (average diagnostic coverage) High
MTTFd (mean time to dangerous failure) Limited to 100 years (cat. 3)
Limited to 2,500 years (cat. 4)
For further characteristics, see the type examination certificate in section 15 Appendix on
page 260.
Proof-testing of the STO function
Comply with the following test intervals in order to reach the specified values:
l For SIL 2, PL d/category 3: 1x per year
l For SIL 3, PL e/category 3: every 3 months
l For SIL 3, PL e/category 4: daily
12.11.1 Electrical data of the STO function
Control inputs STOA/STOB [X3]
Characteristic Value
Nominal voltage 24 V (referred to GNDA/GNDB)
Voltage range 19.2 V… 28.8 V
Permissible ripple 2 % (referred to a nominal voltage of 24 V)
Nominal current 20 mA typ., 30 mA typ.
Switch-on input voltage threshold >= 16 V
Switch-off input voltage threshold < 5 V
For the technical data of the digital inputs DIN6 and DIN7 or of the digital output DIN0, see
the section 12.10 I/O Interface [X1] on page 224.
Product manual BL 4000-C Page 230 of 298
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