Omron CRT1 - 10-2008, Operation Manual

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xix
Operating Environment Precautions 4
!WARNING
Provide safety measures in external circuits (i.e., not in the Slave Units),
including the following items, to ensure safety in the system if an abnormality
occurs due to malfunction of the PLC or another external factor affecting the
PLC operation. (“PLC” includes CPU Units, other Units mounted in the PLC,
and Remote I/O Terminals.) Not doing so may result in serious accidents.
• Emergency stop circuits, interlock circuits, limit circuits, and similar safety
measures must be provided in external control circuits.
• The PLC will turn OFF all outputs when its self-diagnosis function detects
any error or when a severe failure alarm (FALS) instruction is executed.
As a countermeasure for such errors, external safety measures must be
provided to ensure safety in the system.
• The PLC outputs may remain ON or OFF due to deposits on or burning of
the output relays, or destruction of the output transistors. As a counter-
measure for such problems, external safety measures must be provided
to ensure safety in the system.
• When the 24-VDC output (service power supply) is overloaded or short-
circuited, the voltage may drop and result in the outputs being turned
OFF. As a countermeasure for such problems, external safety measures
must be provided to ensure safety in the system.
!WARNING
The CPU Unit refreshes I/O even when the program is stopped (i.e., even in
PROGRAM mode). Confirm safety thoroughly in advance before changing the
status of any part of memory allocated to I/O Units, Special I/O Units, or CPU
Bus Units. Any changes to the data allocated to any Unit may result in unex-
pected operation of the loads connected to the Unit. Any of the following oper-
ation may result in changes to memory status.
• Transferring I/O memory data to the CPU Unit from a Programming
Device.
• Changing present values in memory from a Programming Device.
• Force-setting/-resetting bits from a Programming Device.
• Transferring I/O memory files from a Memory Card or EM file memory to
the CPU Unit.
• Transferring I/O memory from a host computer or from another PLC on a
network.
4 Operating Environment Precautions
!Caution Do not operate the control system in the following locations:
• Locations subject to direct sunlight.
• Locations subject to temperatures or humidity outside the range specified
in the specifications.
• Locations subject to condensation as the result of severe changes in tem-
perature.
• Locations subject to corrosive or flammable gases.
• Locations subject to dust (especially iron dust) or salts.
• Locations subject to exposure to water, oil, or chemicals (including acids).
• Locations subject to shock or vibration.