Live circuit work should always be a last resort. But when necessary, knowing which core tools should be used, is critical.
Guidelines to Measurement Category and Examples
Prevent electrical incidents by making sure your electrical test equipment holds the correct CAT Rating for each job you do, even if it means switching tools throughout the day.
Measurement Category & Examples
CAT 0
- Protected electronic equipment
- Any high-voltage, low-energy source such as a copy machine
- Test equipment not marked with a measurement category
CAT II
- Appliance, portable tools, PCs, TVs and other household and similar loads
- Outlet and long branch circuits
- Outlets at more than 10 meters (30 feet) from CAT III source
- Outlets more than 20 meters (60 feet) from CAT IV source
CAT III
- MC Panels
- Equipment in fixed installations, such as switchgear and polyphase motors
- Bus and feeder in industrial plants
- Feeders and short branch circuits, distribution panel devices
- Lighting systems in larger buildings
- Heavy appliance outlets with short connections to service entrance
CAT IV
- Refers to the "origin of installation", i.e., where low-voltage connection is made to utility power
- Electricity meters, primary overcurrent protection equipment
- Outside and service entrance, service drop from pole to building, run between meter and panel
- Overhead line to detached building, underground line to well pump
Low Voltage Proximity or Non-Contact Voltage Testers
Proximity or Non-Contact Voltage Detectors are a good initial test, testing phase-to-ground. Proximity varies not just by distance but also by the strength of the expanding & contracting magnetic field around an energized conductor.
Digital Multimeters
Multimeters are the best standard test instrument for making accurate contact measurements to determine if a circuit is energized. When choosing the right multimeter, evaluate your basic measurement needs & job requirements.
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