Main electrical panel beside a subpanel with its cover removed

Meter CAT ratings (CAT II, III, IV): choosing a meter and leads that are safe at the outlet and at the panel

IEC 61010 measurement categories describe how big a voltage spike a meter is built to survive at a given point in the electrical system. CAT II covers plug-in loads like appliances and tools; CAT III covers the building's distribution wiring, panels and breakers; CAT IV covers the service entrance, utility meter and outdoor conductors. The category matters as much as the voltage number. Choose a meter for the highest category you might work in, and remember the whole set (meter, leads, clips) is only as good as its lowest-rated piece.

Cross-checked ~10 min easyBrands: All

Before you start

A meter marked only CAT II, or with no CAT rating, should not be used at a panel, breaker or service equipment
Do not use a meter, probe or lead with cracked insulation or exposed metal
CAT ratings on meters are a different thing from NFPA 70E PPE categories

Diagnostic steps

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