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Digital outputs
7 I/O functionality
Instruction book, IQAN-MC3
Disabling DOUT under current detection
It is possible to disable under current detection on individual DOUT:s. This may be
useful when connection a DOUT to a high impedence load, e.g. a relay.
When under current detection is disabled, there are other failure modes that become
undetectable as well. For details on failure modes, see Appendix B, on page 51.
Reset of faults
The reset behaviour of the DOUT is configured in the application file, see IQANdesign
user manual.
Use of DOUT in safety functions
DOUT safe state
The DOUT is assumed to be in a safe state when the output is off; in this state only the
leakage current is delivered, see Appendix A, on page 46.
Minimum current when using DOUT as power driver
This is to ensure that there is no movement when the output is off.
DOUT used as alarm driver in a safety function
The safe state has to apply also when a DOUT is used as an alarm to inform the
operator about a hazardous situation. The IQAN-MC3 can not guarantee that the alarm
is working, but when the DOUT is off, it is capable of detecting if the load is
connected.
This can be used by the application to activate another alarm, or to shut down the
power drivers, or both, to ensure a safe state.
You should also note that there are wiring errors that can only be detected on start-up of
the unit.
Undetected wiring faults
There are DOUT wiring faults that are not detectable by the IQAN-MC3, and there are
faults that are only detected at startup, see Appendix B, on page 51.
MC3-SMR-015:A Minimum current when using DOUT as power driver
When the load connected to the DOUT is capable of initiating a hazardous
movement, it shall be designed so that it is only activated if the current is > 50 mA.
MC3-SMR-016:A DOUT used as alarm drivers
When DOUT is used to implement a safety related alarm function, the application
shall be designed so that it does not rely on a single alarm. The application shall also
be designed so that shutdown of the complete unit also inhibits the hazard that the
alarm is intended to give a warning about.
MC3-SMR-017:A DOUT undetected wiring faults
The application shall be designed so that undetected wiring errors on DOUT are
safe.
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