How to use a megger to test a circuit

Written by eric w. thompson | 13/05/2017
How to use a megger to test a circuit
The megger generates voltage through an electrical circuit to test for proper insulation. (bio battery image by dinostock from

A megger is a type of megohmmeter used for testing electrical insulation in industrial settings. Although a conventional ohmmeter can perform well in most commercial settings, it is incapable of handling the high-voltage capacity of the megger. This is due to the fact that meggers can supply the voltage required to test the large conductors necessary for high-voltage circuits. While megging a circuit is quite easy, the safety issues at hand must be properly addressed, as any major mistakes could result in electrocution.

Cut off power to the circuit to be tested by flipping the breaker and locking it off with a padlock.

Surround the work area with yellow warning tape to protect anyone from accidentally touching the bare end of the cable.

Touch one megger probe to the bare end of the cable, then touch the other probe to the grounding screw of the system in which the cable will terminate.

Turn the megger handle manually and look for a rendering between 2 and 1,000 megohms. Insulation issues are indicated by any reading that is below 2 megohms.

Terminate the bare wire into its intended device using a flathead screwdriver. Remove the yellow warning tape and the padlock. Restore the power to the circuit.

Things you need

  • Electrical wires
  • Padlock
  • Yellow caution tape
  • Flathead screwdriver

Show MoreHide

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.