Safety tips

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Be certain your digital multimeter is rated to handle the conditions found in your work environment.
 

Safety tips

First step: Choose the right tool

Inspect a multimeter before using it

Inspect test probes

Avoid electrical shock

Avoid electrical shock

personal protective equipment (PPE)

Know the hazards

Understand CAT ratings

Always choose a tool rated for the highest category in which it could potentially be used. Reasons why:

CAT rating

Understand voltage ratings

Measurement Category Description Examples
CAT IV

Three-phase at utility connection, any outdoor conductors

Limited only by the utility transformer feeding the circuit

››50 kA short circuit current

  • The "origin of installation"—where low-voltage connection (service entrenc cables) 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.
CAT III

Three-phase distribution, including single-phase commercial lighting

‹50 kA short circuit current

  • Equipment in fixed installations, such as switchgear and polyphase motors.
  • Bus and feeders in industrial plants.
  • Feeders and short branch circuits, devices fed directly from distribution panels.
  • Lighting systems in larger buildings.
  • Appliance outlets with short connections to service entrance
CAT II

Single-phase receptacle connected loads.

‹10 kA short circuit current.

  • Appliances, portable tools, and other household and similar loads.
  • Outlet and long branch circuits.
    • Outlets at more than 10 meters (30 feet) from CAT III source.
    • Outlets at more than 20 meters (60 feet) from CAT IV source.
Measurement Categories IAW IEC/EN 61010-031

Complete the circle of safety by choosing the right tool

Reference:Digital Multimeter Principles by Glen A. Mazur, American Technical Publishers.

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