Electrical outlet tester

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
A receptacle tester for North American wiring

An electrical outlet tester, receptacle tester or socket tester is a device used to verify that an electrical wall outlet is connected correctly. It confirms continuity and polarity of the electrical connections, but does not verify current-carrying ability[1] or electrical safety, which requires impedance testing,[2] insulation breakdown voltage testing and, in ring mains, loop connection testing.[3]

The tester itself is small device containing a power plug and several indicator lights.

Tests performed[edit]

A receptacle tester being used to verify the proper wiring of an outlet. For this particular tester, proper wiring is indicated by the two yellow lights.

The outlet tester checks that each contact in the outlet is connected to the proper wire in the building's wiring. It can identify a number of common wiring errors including phase/neutral juxtaposition and failure to connect ground.

Simple three light testers cannot detect some potentially serious house wiring errors including neutral and ground reversed at the receptacle; in North America there may also be a "bootleg ground", where the neutral and ground pins have been connected together at the receptacle - this, also, cannot be detected. These problems can be detected with a multimeter and a test load, to verify that the ground connection is separate from the neutral and is not carrying normal circuit current, or, more usually, using by a more sophisticated multifunction tester.[4]

Some receptacle testers include an additional test button to check GFCI devices, which supplements the test button within the GFCI, and can be used for testing outlets downstream from a GFCI receptacle. Others include earth loop impedance and other checks.


An early reference that describes the typical circuit was published in Popular Mechanics in the March issue of 1967, and consists of two 27 kΩ resistors, one 100 kΩ resistor, and three NE-51 neon lamp bulbs with 100 kΩ resistors.[5]

See also[edit]


  1. ^ "What Kind of Electrical Tester For My House?". thecircuitdetective.com. Retrieved 2018-12-31.
  2. ^ "Demystifying loop testing". Megger. Retrieved 2018-12-31.
  3. ^ Inspection & testing (Seventh ed.). Stevenage. ISBN 9781849198738. OCLC 902998658.
  4. ^ "Failures in Outlet Testing Exposed". Electrical Construction & Maintenance (EC&M) Magazine. 2013-07-15. Retrieved 2018-12-31.
  5. ^ Ives, Ronald (March 1967). "Three-wire socket checker". Popular Mechanics. 127 (3): 188.

External links[edit]