Kyoritsu Electrical Instruments Works KEW 4506, Instruction Manual

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DANGER : is reserved for conditions and actions that are
likely to cause serious or fatal injury.
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WARNING : is reserved for conditions and actions that can
cause serious or fatal injury.
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CAUTION : is reserved for conditions and actions that can
cause injury or instrument damage.
- Measurement (over-voltage) category -
To ensure safe operation of measuring instruments, IEC 61010
establishes safety standards for various electrical environments,
categorized as CAT O to CAT IV and called measurement
categories.
Higher-numbered categories correspond to electrical environments
with greater momentary energy, so a measuring instrument
designed for CAT III environments can endure greater momentary
energy than one designed for CAT II.
O (None, Other) : Circuits which are not directly connected to the
mains power supply.
CAT II : Primary electrical circuits of the equipment
connected to an AC electrical outlet by a power
cord.
CAT III : Primary electrical circuits of the equipment
connected directly to the distribution panel, and
feeders from the distribution panel to outlets.
CAT IV : The circuit from the service drop to the service
entrance, and to the power meter and primary
overcurrent protection device (distribution panel).
O: Device which is
not directly
connected to the
mains power supply