Last Updated on October 22, 2023 by Kevin Chen
A multimeter is a device used for measuring or testing a variety of electrical and electronic circuits. The multimeter is used to measure the voltage, current, resistance, capacitance, and frequency of electronic components.
Ever wondered how the voltage of live wires is measured or even tested? Multimeters can easily do the job with high efficiency. In this guide, we will discuss how to test the voltage of a live wire using a multimeter.
What is a live wire?
A live wire is a wire that is directly connected to an electrical device. A live wire is different from a neutral or ground wire because it carries a direct current or voltage.
A live wire is usually connected by two or more wires.
The voltage of a live wire is often higher than that of a neutral wire. The difference between the two comes from the fact that a live wire carries an electric current.
How do you test if electrical wires are live?
Let’s say there are several wires and you are not sure which one of them is live. How should you proceed?
There are several ways to test if a wire is live.
Method 1: With the help of a voltmeter
You can use a voltmeter to measure the voltage of the wire. By inserting your multimeter’s black probe into the live wire, you will get an indication on its display that the voltage is more than zero.
Method 2: With the help of a meter bridge (or clamp) If you have a meter bridge or clamp, you can use it to test if there is voltage in any wires. The meter bridge or clamp consists of two electrodes that are joined together by means of an insulator. When you insert your multimeter’s black probe into one electrode, it will show that there is no voltage. However, when you insert the black probe into the other electrode, it will show a voltage.
Method 3: With the help of a multimeter’s continuity tester (or continuity tester) The multimeter’s continuity tester can be used to test if there is voltage in any of the wires.
This is done by inserting your multimeter’s red probe into one wire and its black probe into another wire. If there is no voltage in either of them, you will get an indication on your multimeter that there is no voltage. However, if you can get an indication that there is voltage in the two wires, then the wire that has more voltage than zero will be live.
Steps for using a multimeter to test voltage of a live wire
Let’s now focus on the steps that you should take when testing the voltage of a live wire using a multimeter.
The basic tools that you will need include;
– Wire stripper
– Straight edge
Step One: Take the safety measures
Safety is always of importance when dealing with live wires. One should never work with live wires without taking the proper safety measures. In this case, one needs to ensure that the wire is not touching any other object like a desk or a table. It must also be kept away from any metallic objects like nails, screws, etc.
It is also safer to switch the multimeter from DC to AC mode whenever you want to test the voltage of a live wire. This is because the voltage of a live wire can be very high and you do not want to risk getting an electric shock.
Another safety measure that you should take is to select the right test leads. It is important to pick up a set of test leads that are long enough for you to work with. You will also need them if you want to test the voltage of a live wire from different sides of it.
Step Two: Remove the insulation of the wire
The first step in testing voltage is to remove the insulation from the wire. This can be done by using a wire stripper and cutting it off just below where you will insert your multimeter’s probes onto each end of it.
You can also use a pair of pliers to do this but make sure that you do not cut it too short so that you don’t expose live wires underneath them.
Step Three: Insert the probes of the multimeter
Insert one probe of the multimeter into one end of the wire and insert another probe into the other end. The probes should be placed at such a distance that you can touch both ends with your fingers.
Step Four: Test voltage
Turn on your multimeter to test voltage. When you do this, you will have to let it sit for a few seconds before it starts reading out any readings.
This is done because when you turn on the meter, it takes some time to read out any readings.
Once done, you will notice that there is no reading present in your meter at all. Since there is no current passing through this wire now, there is no voltage present in this wire.
Step Five: Test resistance
Turn on your multimeter and read out the resistance. When you do this, you will be able to see a reading. This is the same as when you test voltage in Step 4.
This is because the multimeter is testing the resistance of the wire and not measuring current in it. This means that there is no current passing through this wire right now either.
Step Six: Inserting probes into other wires
Repeat Steps 3 to 5 on all other wires that need to be tested for voltage or resistance. You can use a pair of pliers or wire cutters if you wish but make sure that you do not cut them too short so that they do not expose live wires underneath them.
How to measure the voltage of a live wire using a digital multimeter
If the steps above seem to be a little bit technical, you can take an easy route-use a digital multimeter. These multimeters can measure both the voltage and resistance of live wires.
Here are the steps to follow when testing and measuring.
Step 1: Insert the leads into the C and COM slots of the multimeter.
Step 2: Set the multimeter to the voltage mode.
Step 3: Place the probes on either side of the wire and connect them to the multimeter’s probes.
Step 4: Hold down either the probe button and read out V (for voltage) or R (for resistance).
If you want to test resistance, then you will need to measure both sides of a wire. If you want to test voltage, then only one side will be needed.
If you do not need to measure resistance, then make sure that both sides are connected in series so that they do not create a short circuit when they meet.
Choosing the right multimeter for testing live wire
Which multimeter is the best for testing live wire? Since there are different types of multimeters, ensure that you choose the best one for the job. The best multimeter for testing live wire is the digital multimeter.
This is because it is capable of measuring both voltage and resistance. You can also use it to check the continuity and the resistance of a wire.
The most common multimeters are analog meters. These come with a needle that moves over a scale when you press the trigger button. They are suitable for checking electrical circuits but not for measuring current, voltage, or resistance because they can only measure voltage and resistance at one point in time, instead of doing this continuously.
If you want to be sure that you get the right type of multimeter, then read reviews by other people so that you can get an idea about what kind of meter they are using when testing live wires. If possible, go and try the multimeter in a shop or a store before you purchase it.
Tips for handling multimeter when testing live wire
Never touch the body of the multimeter when you are testing a live wire. This is because you might get electrocuted and it would be very dangerous. Instead, use an insulated tool to check the wire. This will ensure that you do not get electrocuted.
If you are going to use a digital multimeter for testing a live wire, then make sure that you have some way of grounding yourself. This is because if there is no ground, then you might be affected by high voltage electricity if you touch any part of the meter.
To ground yourself, connect a piece of copper to the meter and connect it to earth ground using an insulated tool or a piece of copper wire.
You should also make sure that you have a good ground before starting to test a live wire. The best way to do this is to use a piece of copper wire and touch it directly to the ground if you have one.
We have covered all the important points about multimeters in this article. It is very important for you to make sure that you know how to read the meter before you start using it for testing the voltage of live wires.
In case you want to buy multimeters for conducting such tests, contact us. We at ICRFQ can guide you through the process of buying a multimeter and will tell you which multimeters are best suited for this purpose.
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