How to Test for Live Wire with a Multimeter

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A word of caution: testing wires to determine if they are live or not could be risky, especially if you are not a professional. It is important that you turn off your breaker at the main panel before opening any electric box in your home. Also, do not work on a live wire in any circumstance! 

You will find many different ways to test and identify if an electrical cable is live. You may need to do this if you’re installing a new light switch, renovating your home, or suffering from an electrical fault. Whatever the case, you must perform the task with utmost care and great attention to detail.

Remember that even a small lapse in judgment could put you at risk of grave injury or death. That’s especially true if you’re confused by the wiring’s layout or the wiring is disorganized because of poor workmanship done by the previous technician.

If you’re not totally confident in your skills to deal with an electrical system, it will help if you hire an expert who will do the job right. However, if you like to proceed, here’s everything you need to know. 

What is a Live Wire? How Does it Work? 

A live wire is an electrical wire where electrical current flows. A live wire is considered positive, while a neutral wire is negative. These live wires are considered to have the highest number of voltages and could prove deadly if you come in contact with them.

To safeguard you from any deadly accidents, most electrical circuits are presented with an Earth wire. 

What is the Best Way to Test for Live Wire?

You will find two different tools you can use to test for live wire. You can use a non-contact voltage tester or a multimeter. In this case, we’ll dig deeper on using a multimeter. 

A digital multimeter is an electronic device utilized to measure amps, resistance, and voltage. You can alternate between different electrical units on the fly by just turning the knob. It’s a very convenient yet versatile device required every time you need to measure electricity.

Purposely created, it’s an indispensable digital device that excels in measuring Ohms, Ampere, and Voltage in wires. That’s why it’s also referred to as a multi-tester or VOM (Volt-Ohm-Meter). 

To test a wire or other piece of electrical equipment, you utilize the two probes connected to the device: one black (negative) and the other red (positive). Before checking whether the cable is live, you need to switch the power off. 

No matter what reading the tool picks up is conveniently shown on the LCD screen. 

So, when would you require a digital multimeter over a non-contact voltage tester? Well, these devices are efficiently practical if you work or live on an older premise, and you like to determine if an equipment ground wire is connected to the grounds within the system.

You can also utilize the non-contact voltage tester first to check an electrical outlet before investing in the wires. 

Proper Way to Use a Multimeter When Testing for Live Wire

Here comes the moment of truth. Before we jump into the process and steps, here’s a safety precaution you need to keep in mind: 

  • Don’t use a multimeter to apply power to the circuit while you measure the resistance
  • Don’t forget to discharge and de-energize the circuit before connecting or disconnecting the digital multimeter
  • Don’t touch a live wire with your bare hands. Always wear an insulating glove even if you simply like to fix or move the cable
  • Switch your multimeter from DC mode to AC mode every time you like to measure an electrical value in your AC circuit

Follow the steps below to test for live wire using a multimeter.

  1. Find the proper power outlet 

Ensure you find the power outlet where the wire you like to test leads. Take your tester and turn it on. Insert your tester into the outlet’s positive side.

  1. Use the tester to check for power

Insert your tester on the outlet’s negative side. The tool should not show power because that’s the negative terminal. 

  1. Test the live wire with a multimeter

Turn your meter on and place the probes in it. Plug one probe into the ground wire and the other probe into the positive hole of the socket. Leave one probe into the ground hole and change the other probe in the negative hold. Put one probe in the positive hold and the other probe in the negative hole.

You should receive a reading of at least 100 or 120 volts during the ground and live wires test. 

BONUS: Importance Safety Tips You Should Not Ignore 

Let’s admit it. This is one of those scenarios where having a quality digital multimeter could pay off. The most crucial feature for this kind of task is an overall level of safety. 

Consider these safety tips:

  • Learn the wire type you’re testing

Wires could have smaller or four wires inside them. You can receive an accurate reading in that case, but there’s also a possibility that you won’t. Investigate your home’s layout and learn where the wire leads to.

  • Get a multimeter with a high safety rating

When using a multimeter, always go for the model with the highest security settings. Indeed, this is common sense, but more people often ignore this aspect. 

  • Use protective rubber gloves

Are you testing a live wire for the very first time? Then you can’t underestimate the value of using a protective glove. These items are utilized by specialists when working with electricity in environments or scenarios where there’s a chance of a powerful electrical discharge. 

Of course, you won’t be doing that. However, these gloves will provide you the protection you may need. 

Final Thoughts

Your life is precious, so don’t risk it for anything. Suppose you are still not confident doing this test on your own despite the information you’ve read above; feel free to call an expert electrician to help you.

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