Peter Walsh, PE
Arc flash hazard awareness is a growing trend. Testers and meters are in the mix of everyday equipment that should be examined for safety.
OSHA and NFPA 70E, "Standard for Electrical Safety in the Workplace," promote new requirements for safe meters. For instance, paragraph 110.4(A)(2) of NFPA 70E refers to using test equipment and their accessories with proper ratings for the work.
A CAT I rating on a meter means it is only rated for use on appliances or bench-top equipment testing. Most electricians use their meter on power distribution wiring that requires a higher CAT rating. The CAT rating is paired with a maximum voltage. The same meter might have a CAT I rating for 600 volts and a CAT II rating for 250 volts.
Using a CAT rating insufficient for the circuit is hazardous and is not in compliance with OSHA and NFPA 70E. Insufficiently rated meters can explode or arc over causing an arc flash. If the meter is equipped with computer connection cables or other accessories, they can cause similar dangers. Meters and testers should be rated for the conditions of use.
An example of a safe clamp-on meter is the AEMC Model 407. It has a CAT IV rating up to 1000 volts. This is suitable for service anywhere in a facility with a power distribution system not exceeding 1000 volts.
This clamp-on records up to 1000 measurements and can download them through Bluetooth technology, which doesn't require hazardous connectors on the instrument. Although this meter has extensive additional features, it has the ratings and functions to make electrical measuring safe.
Photo courtesy of AEMC