Safety Tip #3: Before starting any job, confirm that the DMM and test leads are rated for the category and voltage level appropriate for the work

Category ratings, safety standards

Electrical measurement category ratings are defined by the safety standard, IEC 61010, and are separated into four distinct category ratings, CAT I, CAT II, CAT III or CAT IV Other requirements of IEC61010 to be familiar with include those relating to transient test, dielectric withstand voltage, clearance spacing, exposed metal probe tips, impact and markings.

The NFPA 70E standard also requires that the test tools used on the job be rated for the environment they will be used in. This applies to both the meter and the test leads/probes, and any PPE (Personal Protective Equipment) necessary for safe measurements. PPE ratings are somewhat different than CAT ratings.

IEC 61010 Electrical measurement category ratings for test tools

Important note: CAT ratings on test tools are different than hazard/risk category ratings on PPE gear. CAT ratings are determined by the potential transient impulse in the workplace that a connected test tool might experience. PPE requirements are determined by the surface energy level a user might experience.