How to use a multimeter to test the voltage of live wires

How to Use a Multimeter to Test the Voltage of Live Wires?

If you use multimeters and clamp meters on a regular basis, you know that testing the voltage can sometimes be fun and engaging work. 

However, you have probably found yourself in a situation where you need to test the voltage of live wires at least once.

If you are in this situation right now, you have found the right article for you.


But before we begin, a disclaimer.


!!! The testing the voltage of live wires can cause serious injury or death if you don’t know what you are doing !!!

!!! If you are not an experienced professional, do not attempt to do this !!!

This article serves for informational purposes only.

Make sure that the wire is live with an electrical tester

First of all, we need to make sure that the wire we are planning to test with a multimeter is really under voltage. 

We can use a cheap electrical tester for that. You can get one online or from any tool shop.

Locate the correct power outlet

  1. Make sure that you locate the power outlet where the wire that you want to test leads.
  2. Take the tester and turn it on.
  3. Place the tester into the positive side of an outlet.

If everything is OK, the tester should give you a visual or sound indication that the wire is live.

Use the tester to check for power

Place the tester on the negative side of the outlet. The tester shouldn’t indicate power since that is the negative terminal. Please take your location into account when doing this.

Power sockets in the United States differ greatly than those in the European Union. It can be easy to make a mistake when doing this.

If your tester isn’t showing you any indication whether the wire is live or not, test another power socket for which you are absolutely sure that has power. A great example for this is the socket where your TV is plugged in. 

Plug the TV out and test the socket with the tester. If a tester shows that the second socket has power, the first socket isn’t live. If a tester doesn’t detect any power running through the second socket, and you are absolutely sure that you are doing everything right, then the tester must be broken.

Since you are now certain that the wire you want to test has power, we can continue on with the test. The easiest way to test wire for voltage using a multimeter is by testing the power socket because you only need to plug the probes in. 

Anything else is probably beyond for an average DIY enthusiast, and in the case that you do need to conduct an advanced test, I highly recommend that you call in a professional.

Test the wire using a multimeter

Turn your multimeter on and plug the probes in the multimeter.

The average power of the current in household grids in the United States is one hundred and twenty volts, while the power of the household grid in Europe is two hundred and twenty volts. Either way, you will need to set your multimeter to AC voltage, two hundred volts setting.

If you have a European socket with two holes, you will need to place the probes in the holes. Wait for a second, and you should get a reading of the voltage in a circuit. It doesn’t matter what probe you place in which hole because this is AC current that is flowing through the household grid. 

You will get a correct reading regardless. The reading should be around two hundred and ten or two hundred and twenty volts.

If you have a power socket designed for the United States market, here’s what you’ll need to do.

  1. First, insert one probe into the ground wire and one probe into the positive hole of the socket.
  2. After that, you should leave one probe in the ground hole, and replace the other probe in the negative hole.
  3. After you did that, you should place one probe in the positive hole and another probe in the negative hole.

You should get a reading of around one hundred and ten or one hundred and twenty volts during the ground and live wires test and during neutral and live wires test on the United States type socket.

When you test the power between ‘ground’ and ‘neutral’ socket, you should get a value of zero volts.

Test the voltage of live wires using a clamp meter

If you don’t have a multimeter at hand, you can always use a clamp meter.

If you haven’t read one of our articles on using a clamp meter, I will give you a short tutorial on using the clamp meter to measure voltage here.

Use an AC line separator in combination with the clamp meter:

  • If you don’t have a wire that you can clamp with the meter, you will need to use an AC line separator.
  • Plug the separator in the socket and turn the clamp meter on.

Set the clamp meter on the desired setting:

  • Clamp meters can be used just like multimeters, except clamping.
  • Set the clamp meter on voltage and clamp the AC line connector on the first hole near the wall. The second hole gives you a reading multiplied ten times, so we don’t want that now. There is a small possibility that your clamp meter won’t be able to do this. The reason for that lies in the clamp meter itself since clamp meters can measure either AC or DC voltage.
  • Some clamp meters can measure both, but that’s not the industry standard.

Test the live wire using an AC line separator:

After you have done that, you should get a reading. This is also the safest way to use a clamp meter to measure the voltage of live wires.

You can also measure the voltage of live wires with probes. Some clamp meters have that possibility. In this case, the entire process is the same as using a multimeter.



This is one of those situations where having a quality multimeter could really pay off.

The most important feature for this type of job is an overall level of safety.

Use protective rubber gloves

If you are doing this for the first time, I recommend that you get yourself rubber gloves designed specifically for protection against high powered electric shocks.

Such pieces of equipment are used by professionals when working with electricity in situations and environments where there is a possibility of a powerful electrical discharge. Although you won’t be doing that, these gloves will offer you all the protection you might need.

rubber gloves

When we add into account the fact that you will probably be using a multimeter with safety ratings and fuses, you are safe and good to go.

Get products with high safety ratings

This is more of a general tip than it is related to this article, but it can pay off. When getting a multimeter or a clamp meter, always aim for the model with higher security settings.

Yes, this is common sense, but people often neglect this. When doing something like this, such a thing could literally save your life.

CAT ratings and fuses

Your multimeter should have at least one fuse (a high quality ceramic one, if possible) and a CAT III or CAT IV safety rating. A CAT rating guarantees you that your multimeter will be able to protect you in case that something goes wrong while you are testing the conductor under power.

It could also pay off to have a multimeter with a blast shield on the inside and a thick rubber protective shell. In case that the multimeter overloads and explodes, the blast shield will make sure that nothing pops out. The rubber shell will do the same, but it can also protect you from the current.

Protective caps

If you have probes that allow for caps that reduce the metal area on the tip of your probes to be placed on them, now is an excellent time to use them. 

These caps will minimalize the possibility of accidents.

testing live wires

Know what type of wires are you testing

You should always know what type of wires you plan on testing.

Some wires can have four or smaller wires inside.  In such a case, you could get an accurate reading, but there’s also a chance that you won’t. Study the layout of your home and know where does the wire lead to.


You shouldn’t risk your life and your wellbeing for anything. If you don’t feel confident enough to do this, contact a professional electrician.

I hope that you will get a precise reading and that you will do this safely.

I know that I was amazed at the simplicity of this when I first tried it. But then again, I had a friend of mine who is a technician to show me how to do this. With a little bit of practice, I am certain that you will be able to do this too.

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