Omron CP1H-CPU - 05-2006, Operation Manual

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xxiii
Safety Precautions
3
• 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 or 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-V DC output (service power supply to the PLC) is over-
loaded 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
Fail-safe measures must be taken by the customer to ensure safety in the
event of incorrect, missing, or abnormal signals caused by broken signal lines,
momentary power interruptions, or other causes. Not doing so may result in
serious accidents.
!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
Confirm safety at the destination node before transferring a program to
another node or editing the I/O area. Doing either of these without confirming
safety may result in injury.
!Caution Tighten the screws on the terminal block of the AC power supply to the torque
specified in this manual. The loose screws may result in burning or malfunc-
tion.
!Caution Do not touch anywhere near the power supply parts or I/O terminals while the
power is ON, and immediately after turning OFF the power. The hot surface
may cause burn injury.
!Caution Pay careful attention to the polarities (+/-) when wiring the DC power supply. A
wrong connection may cause malfunction of the system.
!Caution When connecting the PLC to a computer or other peripheral device, either
ground the 0 V side of the external power supply or do not ground the external
power supply at all. Otherwise the external power supply may be shorted
depending on the connection methods of the peripheral device. DO NOT
ground the 24 V side of the external power supply, as shown in the following
diagram.
24 V
0 V 0 V
Non-insulated DC power supply
0 V
Peripheral device
FG FG
CPU Unit
FG
Twisted-pair
cable
FG