Per IEC61010-1 and IEC60664:
Measurement Category IV (CAT IV) is for measurements performed at the
source of the low-voltage installation. Examples are electricity meters and
measurements on primary overcurrent protection devices and ripple control
units.
Measurement Category III (CAT III) is for measurements performed in the
building installation. Examples are measurements on distribution boards,
circuit-breakers, wiring, including cables, bus-bars, junction boxes, switches,
socket-outlets in the fixed installation, and equipment for industrial use
and some other equipment, for example, stationary motors with permanent
connection to the fixed installation.
Measurement Category II (CAT II) is for measurements performed on circuits
directly connected to the low voltage installation. Examples are measurements
on household appliances, portable tools and similar equipment.
WARNING!
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To reduce the risk of fire or electric shock, do not expose this product to
rain or moisture. To avoid electrical shock hazard, observe the proper
safety precautions when working with voltages above 60 VDC or 30 VAC
rms. These voltage levels pose a potential shock hazard to the user.
Keep your hands/fingers behind the hand/finger barriers of the test
probes that indicate the limits of safe access of the hand-held part during
measurement. Inspect test probes, connectors, and probes for damaged
insulation or exposed metal before using the tester. If any defects are found,
replace them immediately.
The voltages marked on the tester are nominal voltages or nominal voltage
ranges. The tester shall only be used on installations with the specified
nominal voltages or nominal voltage ranges.
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