5
Safety Information
Measurement categories
To ensure safe operation of measurement 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.
• Using a measuring instrument without categories in an environment designated
with the CAT II to CAT IV category could result in a severe accident, and must
be carefully avoided.
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 (xed 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).
Outlet
CAT II
Internal Wiring
Distribution Panel
Service Entrance
Service Drop
CAT IV
Power Meter
CAT III
Fixed Installation
10
9
8
7
6
5
4
3
2
1
Appx. Ind.
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