SIGMATEK SNC 021, Руководство пользователя

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S-DIAS SAFETY SNC INCREMENTAL ENCODER SNC 021
02.12.2019 Page 29
12 Important Notes for Two-channel Application
When using the SNC 021 module in compliance with SIL 3 or SIL CL 3 according to EN
62061 and PL e , Cat. 4 according to EN ISO 13849-1, it must be taken into consideration
that for 2-channel application, a part of the possible wiring errors can only be detected by
comparing the measurement results of both encoders in the Safety application of the Safe
CPU. The inversion of signal lines A+ with A- as well as B+ with B- are one of these errors.
Mechanical errors, such as a detached coupling can also be detected only in the Safety
application of the Safe CPU.
To meet the requirements of the diagnostic coverage ratio, both encoders must be
synchronously monitored in the Safety application of the Safe CPU.
For synchronous monitoring, the functional Safety block SF_SkewMonitor (see chapter
“Numerical Function Blocks” in the SafetyDesigner tool help) must be placed in the Safety
project and used according to the documentation.
The inputs S_ChnValue1 and S_ChnValue2 of the functional Safety blocks must be wired
with the input information _Chn1Value and S_Chn2Value (synchronous monitoring of the
position) or alternatively, with S_Chn1Speed and S_Chn2Speed (synchronous monitoring of
the speed) of the SNC 021 module.
The required tolerance must be defined by the user. During synchronous monitoring via the
position, it must be taken into consideration that if there is the possibility of a position overflow,
the scaling parameter can cause position jumps. In such a case, the scaling parameter for
calculating the position should be left at the default settings (factor and divisor
are 1), or synchronous monitoring performed using the speed.
If the system is not in Safe mode, synchronous monitoring must be performed
according to the previously mentioned criteria
Si le système n'est pas en mode Safe, une surveillance synchrone doit être effectuée
selon les critères mentionnés précédemment.
If all mechanical error sources can be excluded due to the coupling type and the type of
encoder used (e.g. defective encoder mechanics), monitoring the direction of both encoders
is then sufficient.
This can be run in the Safety application using the functional Safety block
SF_DirectionMonitor (see chapter “Numeric Function Blocks” in the SafetyDesigner tools
help) and in this case, performed for both encoders.
If synchronous monitoring is not performed in the Safety application as described
here, the machine manufacturer must then prove that the requirements of SIL 3 or
SIL CL 3 according to EN 62061 and PL e, Cat. 4 according to EN ISO 13849-1/-2 are
met if required for the machine.