How to Use a Multimeter to Test an Outlet

With help from Mr. Electric, you can learn how to test your outlets with a multimeter– the go-to tool for diagnosing electrical problems.

Dead outlet? Purchasing a multimeter, the go-to tool for diagnosing electrical problems, could allow you to investigate and address outlet issues. Not sure how to test an outlet? Read on, and the experts at Mr. Electric will help you learn how to diagnose common outlet problems with a simple multimeter test.

What Can a Multimeter Tell You?

The reading on a multimeter can help you determine

  • If power is actually reaching an outlet.
  • If the outlet is properly grounded.
  • Whether wiring within the outlet is reversed.

How to Use a Multimeter to Test an Outlet

  1. Learn the essentials of outlet testing safety.
    Because you will be performing these tests on a live outlet, ensure safety by holding both meter probes in the same hand. This will prevent shock from passing through your body. Never allow the metal portion of the probes to brush each other or touch, as this can create a dangerous short circuit.
  2. Get to know outlet geography.
    An outlet has three slots: one for hot, one for neutral and one for ground. The rounded half circle is the ground, the longer slot (left) is the neutral and the shorter slot (right) is hot.
  3. Adjust your multimeter.
    Set your meter to measure voltage. Select the alternating current (AC) function on the multimeter, which is often depicted with a wavy line. (The DC function will have a solid and a dashed line.)
  4. Connect the leads.
    Push the short, thick connector (called a ‘banana plug’) of the BLACK lead into the connector labeled ‘COM’ (it may have a minus “-” sign beside it). Plug the RED connector labeled with a “+” or horseshoe symbol (the Greek letter Omega).
  5. Measure the voltage to determine if the outlet has power.
    Using the same hand, insert a probe into each vertical slot on the outlet. Red goes in the smaller slot, black into the larger one. A properly functioning outlet will give a reading of 110-120 volts. If there is no reading, check the wiring on the outlet.
  6. Determine if the outlet is properly grounded.
    Remove the black lead and place it in the ground (u-shaped) outlet slot. The reading should remain the same. If it doesn’t, the outlet is improperly grounded – or the wiring is reversed (see next).
  7. Check if the wiring is reversed.
    Place the red lead into the left-hand slot and the black lead into the ground. If no reading, the outlet is not grounded. If you get a reading, the wiring is reversed. This won’t affect simple equipment like lamps but can cause issues for more sophisticated appliances.
  8. Determine problems with a particular appliance.
    Learn “How to Make Electrical Tests” with the help of Mr. Appliance, a Neighborly company.

Outlet issues? Avoid a hair-raising electrical experience. Contact Mr. Electric today.

This blog is made available by Mr. Electric for educational purposes only to give the reader general information and a general understanding on the specific subject above. The blog should not be used as a substitute for a licensed electrical professional in your state or region. Check with city and state laws before performing any household project.