Hioki FT4310, Instruction Manual, Page: 11 / 72

7
Safety Information
Measurement Categories
To ensure safe operation of measuring instruments, IEC 61010
establishes safety standards for various electrical environments,
categorized as CAT II to CAT IV, and called measurement
categories.
DANGER
• Using a measuring instrument in an environment
designated with a higher-numbered category than
that for which the instrument is rated could result in
a severe accident, and must be carefully avoided.
• Never use a measuring instrument that lacks
category labeling in a CAT II to CAT IV measurement
environment. Doing so could result in a serious
accident.
CAT II: When directly measuring the electrical outlet receptacles of
the primary electrical circuits in equipment connected to an
AC electrical outlet by a power cord (portable tools, household
appliances, etc.)
CAT III: When measuring the primary electrical circuits of heavy equipment
(fixed installations) connected directly to the distribution panel, and
feeders from the distribution panel to outlets.
CAT IV: When measuring the circuit from the service drop to the service
entrance, and to the power meter and primary overcurrent
protection device (distribution panel).
T
Outlet
CAT II
Internal wiring
Distribution panel
Service entrance
Service drop
CAT IV
Power meter
CAT III
Fixed installation
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Appx.
Index