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Safety Precautions 3
!WARNING Provide safety measures in external circuits (i.e., not in the Programmable
Controller), including the following items, in order to ensure safety in the sys-
tem if an abnormality occurs due to malfunction of the PLC or another exter-
nal factor affecting the PLC operation. 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 deposition 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.
!WARNING When transferring programs to other nodes, or when making changes to I/O
memory, confirm the safety of the destination node before transfer. Not doing
so may result in injury.
!Caution Execute online edit only after confirming that no adverse effects will be
caused by extending the cycle time. Otherwise, the input signals may not be
readable.
!Caution Tighten the screws on the terminal block to the torque specified in the opera-
tion manual. The loose screws may result in burning or malfunction.
!Caution When connecting the PLC to a personal computer or other peripheral device,
either ground the 0-V side of the PLC or do not ground the PLC at all.
Although some grounding methods short the 24-V side, as shown in the fol-
lowing diagram, never do so with the PLC.
24 V
0 V 0 V
0 V
PC Peripheral device
Non-isolated DC power
supply
INCORRECT Grounding: Shorting the 24-V side of the Power Supply
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