Testing & TroubleshootingQuestion 482 of 521
You will take voltage measurements at the line terminals of a 240 V main service panel. What minimum measurement category (CAT) rating should your meter and leads carry for this location?
a.CAT I
b.CAT II
c.No CAT rating is needed for 240 V
d.CAT III (or CAT IV)
Explanation
Service-entrance and main-panel/feeder work sits at CAT III-IV because available fault energy and transient spikes are highest there. CAT I is for protected electronic circuits and CAT II for cord-and-plug loads at receptacles. Using an under-rated meter risks an arc-blast if a transient occurs.
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