Which category rating would be appropriate for voltage measurements at service equipment in an industrial facility?

• A. CAT II
• B. CAT I
• C. CAT III
• D. CAT IV

Answer: (C)

Category ratings indicate how much transient voltage a meter and its leads can safely withstand in different parts of an electrical installation. For service equipment inside an industrial facility—like distribution panels, feeders, and switchgear—the measurement location is at the distribution level inside the building. These points can experience higher transient events than simple consumer outlets, so the instrument and its leads must be rated for CAT III to protect you during voltage measurements. Tools rated CAT III are specifically built to handle the kind of transients you encounter within a facility’s distribution system, making them the appropriate choice. (CAT IV would be for service entrances and outdoor primary supply connections, which are beyond this measurement scenario.)