Mitsubishi Electric MELCEC Q Series User Manual page 3

Before using the product, please read this manual and the relevant manuals carefully and pay full attention
to safety to handle the product correctly.
In this manual, the safety precautions are classified into two levels: "
WARNING
CAUTION
Under some circumstances, failure to observe the precautions given under "
serious consequences.
Observe the precautions of both levels because they are important for personal and system safety.
Make sure that the end users read this manual and then keep the manual in a safe place for future
reference.
[DESIGN PRECAUTIONS]
Configure safety circuits external to the programmable controller to ensure that the entire system
operates safely even when a fault occurs in the external power supply or the programmable
controller. Failure to do so may result in an accident due to an incorrect output or malfunction.
(1) Configure external safety circuits, such as an emergency stop circuit, protection circuit, and
protective interlock circuit for forward/reverse operation or upper/lower limit positioning.
(2) When the programmable controller detects the following error conditions, it stops the operation
and turn off all the outputs.
• Overcurrent or overvoltage protection of the power supply module is activated.
• The CPU module detects an error such as a watchdog timer error by the self-diagnostic
function.
All outputs may turn on when an error occurs in the part, such as I/O control part, where the
CPU module cannot detect any error. To ensure safety operation in such a case, provide a
safety mechanism or a fail-safe circuit external to the programmable controller. For a fail-safe
circuit example, refer to Chapter 9 LOADING AND INSTALLATION in this manual.
(3) Outputs may remain on or off due to a failure of an output module relay or transistor. Configure
an external circuit for monitoring output signals that could cause a serious accident.
In an output module, when a load current exceeding the rated current or an overcurrent caused by a
load short-circuit flows for a long time, it may cause smoke and fire. To prevent this, configure an
external safety circuit, such as a fuse.
SAFETY PRECAUTIONS
(Read these precautions before using this product.)
Indicates that incorrect handling may cause hazardous conditions,
resulting in death or severe injury.
Indicates that incorrect handling may cause hazardous conditions,
resulting in minor or moderate injury or property damage.
WARNING
A - 1
WARNING" and "
CAUTION" may lead to
CAUTION".