How to Use a Multimeter to Test an Outlet

How to Use a Multimeter to Test an Outlet

It’s recommended to check your electrical outlets before connecting your new home entertainment system, smart TV, a computer or any other electronic.

Incorrectly wired outlets and poor ground connections can either cause your sensitive electronics to behave unpredictably and in weird ways or damage them.

With an affordable digital multimeter, you can test your outlets to ensure they’re functioning optimally. A multimeter is the most versatile tool in a toolbox. Therefore, you need to invest in one and have it within reach for easy access whenever the need to use it arises.

What is a Multimeter?

Also known as digital voltmeters or volt-ohm meters, multimeters find use in varied electrical measurement application areas.

A typical multimeter features a dial at the center, a large LCD display at the top and three test probe connection set beneath. The dial rotates from one function to another. The AC voltage setting is used for testing electrical outlets.

what is a multimeter

Although you can also measure continuity, gauge resistance, circuit logic, frequency, capacitance and current, voltage is the most important measurement a multimeter takes.

In fact, all the other measurements are usually derived from voltage readings. Multimeters use resistors to take voltage readings.

It’s also important to note that there are two types of multimeters: analog and digital. Multimeters are also designed for use in various application areas, including industries. Therefore, their prices vary based on their functionality. You just need a meter designed for simple use to test your electrical outlets.

Step-By-Step Guide to Using a Multimeter to Test Electrical Outlets

Connect the Leads

The test leads are black and red. On one end is a banana plug, a short and thick connector while the other end has rigid plastic handles in the form of narrow and pointed metal probes.

Find the connector labeled ‘COM’ on your multimeter and push the banana plug of the black lead inside it to make a connection. Most often, this plug is the one at the center with a minus sign next to it.

Find another connector with a ‘V’ sign for voltage and an omega (resembles a horseshoe) for resistance. It looks like this VΩmA. It might also have a plus sign next to it. Plug the red lead into it to make a connection.

multiple electrical outlets not working?

Select the Right Function

Find the AC voltage setting on your meter’s dial. Whereas some multimeters have DC and AC voltage settings at different positions on the dial, others use a single setting with a button for toggling between the two. If you’re not sure, reference your user manual for detailed instructions.

Some multimeters also have different settings for voltage ranges or levels. If yours has a similar setting, select a setting with at least 100 volts. If you’re not sure, select a setting with the highest voltage range. However, this can result in inaccurate readings.

With modern multimeters such as Fluke 87-V (you can check it out on, you don’t have to do anything as they’re built to auto-detect voltage ranges or levels.

Check the Test Leads for Safety

Electrical outlets have live power, making them risky. Check that the test leads are in good condition before you begin testing your outlets. Your safety comes first.

Is the insulation intact? Are the wires frayed? Are the probe ends wobbly or loose? Are there visible damages or cracks on the insulated handles of the probes?

Never brush the probes against each other or touch their metallic parts when taking measurements. Doing so would create a short circuit that can get you electrocuted.

Test Your Electrical Outlets

Many outlets are polarized with one outlet slot being wider than the other. Whereas the smaller, narrower slot carries live voltage, the other wider slot is ground or negative.

Insert the red lead into the smaller, narrower slot and the black lead into the wider slot to make a connection. The standard voltage range for outlets in North America is 109 to 121 volts. Your multimeter reading on the display should lie within that range.

If there’s a minus sign in front of the voltage number on your display, it indicates a reversed outlet polarity. Although you can use such an outlet with simple electronic gadgets such as lamps, connecting sophisticated electronics that consume a lot of power can cause problems.

Disconnect the black probe from the wider outlet slot. Connect it to the round ground connection at the outlet’s bottom. Your voltage reading should be similar to the one above.

Disconnect the two probes and insert one into the wider neutral outlet slot. Connect the other to the round ground connection by inserting the second probe into the slot. Your voltage reading should be zero.

Why Use a Multimeter to Measure Voltages?

Multimeters are accurate. They’re built to reduce interpolation and reading errors.

The meters have auto-polarity functions to ensure wrong polarity on your electrical outlets don’t cause problems during tests. It also eliminates parallax errors; reading different values if readings are taken from different angles.

testing voltage with a multimeter

Multimeters’ displays feature no moving parts and thus rarely fail due shock or wear. They also support fast display of measurements for easy readings.

Furthermore, readings can be processed further if need be and they cause low meter loading during tests. The small sizes of multimeters render them highly portable.


With the versatile use of a multimeter, it’s important to have at least one in your toolbox. Electronics are expensive, hence must be cared for properly.

Making sure that your outlets have the right voltage rating before connecting your gadgets is one of the many ways you can care for your electronics. As a result, you get to use them for many years as the manufacturer intended.

Similarly, you need to care for your multimeter and use them properly as instructed by the manufacturer. Always follow the instructions on the user manual to ensure your meter works optimally and don’t get damaged.

1 thought on “How to Use a Multimeter to Test an Outlet”

  1. So what does it mean when when the readings differ? Specifically hot to ground is 8 volts less than hot to neutral and neutral to ground shows 6 volts?

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