Glossary - Siemens SIMATIC S7 F Manual

Glossary

1oo1 evaluation
1oo2 evaluation
A
Acceptable risk
AK requirement classes
C
Channel fault
Cyclic redundancy check
(CRC)
D
Dark period
Diagnostic coverage level
Diagnostic test interval (DTI)
Fail-Safe Systems
A5E00085588-03
Type of sensor evaluation: In 1oo1 evaluation, there is one sensor and it
is connected to the module via a single channel.
Type of sensor evaluation - In 1oo2 evaluation, the signal states of the
inputs are compared internally (equivalence or non-equivalence).
The acceptable risk is the highest acceptable risk of a certain technical
procedure or state.
Requirement classes (AK) in accordance with DIN V 19250 (DIN V VDE
0801)
Categories or levels describing safety requirements in order to avoid and
deal with faults. The fail-safe signal modules can be used in safety mode
up to requirement class AK6.
Channel-related fault (e.g. wire break or short circuit). In channel-specific
passivation, the relevant channel is automatically depassivated after the
problem is eliminated.
A test procedure to check the integrity of data. By means of a generator
polynominal, a check sum is formed that is characteristic for the relevant
data volume in the sense of being a signature. A CRC check sum is
formed, for example, for the process values contained in the safety frame
or for the safety-related parameters of the fail-safe signal modules.
Dark periods occur during switch-off tests and complete bit pattern tests.
This involves test-related 0 signals being switched to the output by the
fail-safe output module while the output is active. The output is then
switched off briefly (dark period). A sufficiently slow actuator does not
respond to this and remains switched on.
Percentage of hardware faults that are detected by automatic diagnostic
tests.
Interval between online tests that detect faults in a fail-safe system with a
specific diagnostic coverage level.
Glossary-1