Whether you are testing batteries or making sure your wiring job was done well, a voltmeter is a must-have item. If you’re not a licensed electrician, the thought of playing with electricity might terrify you. But if you know how to use a voltmeter, you have nothing to fear! We’ll walk you through it so you can measure those volts with confidence.
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What Is a Voltmeter? |
A voltmeter, as its name implies, is a device that measures the voltage in an electrical circuit. Voltmeters are handheld devices that won’t take up much space in your tool kit.
Besides voltage, you may also want to measure the amperage in the circuit. A standard voltmeter usually doesn’t have this feature, but more advanced devices called “multimeters” do. Consider this before you buy a new voltmeter or multimeter.
● What Types of Current Can a Voltmeter Read?
There are two types of current, AC and DC. AC, or alternating current, changes direction at a specific rate measured in hertz. DC, on the other hand, produces a constant one-way current. Most voltmeters should be able to read the voltage in both types, but make sure yours has this feature before you connect it to a circuit.
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AC is what you find in your walls at home. DC is usually used by smaller devices, like your mobile phone. |
● What Are the Parts of a Voltmeter?
Voltmeters essentially consist of three main components. Let’s take a look at each of them.
 First, there is the device itself, which may have switches or knobs to allow you to fine-tune its settings. It’s usually no bigger than a thick mobile phone. You can stuff it in your pocket or often clip it to your tool belt. The device will also have a simple display that tells you the voltage. If it’s an older model, the display could be analog with a red needle that indicates the voltage. Otherwise, it will be digital, with an LCD or LED display that reads the voltage from the circuit. |
 Next are the probes, which may be hard-wired into the device or detachable. Detachable probes are preferable, since you can easily replace a broken probe. Just don’t lose them! One of the probes will be red, for the positive terminal. The other will be black for negative. |
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Finally, there will be some kind of power source. Usually a voltmeter uses a nine-volt battery to power the display on a digital model. |
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Is There a Need to Know How to Use a Voltmeter? |
Obviously, if you’re an electrician, then you absolutely must know how to use a voltmeter. But for the rest of us, when would this ever come in handy? More often than you would suspect.
Stay Safe First of all, you can use a voltmeter to ensure that the electricity is in fact switched off when you are doing electrical work. Especially when dealing with old construction, switches and wires may not always be reliable. Use your voltmeter to make sure you won’t get a nasty shock. |
DiagnosticsVoltmeters make for great diagnostic tools as well! If an appliance isn’t working as it should be, you should test the power outlet before testing the device itself. That machine might not be getting the right amount of voltage, and that can lower its performance. A simple check with the voltmeter will tell you if the circuit or the machine is to blame. |
Manage Electronics If you do any kind of work with small electronics, such as soldering your own circuit boards, then a voltmeter is your best friend. PC repair workers should have one handy at all times. Circuit boards frequently have several different voltages on them at any time, and a malfunctioning component can only be detected with a voltmeter. |
MechanicsCar mechanics also need to have a voltmeter handy. Even though we tend to think of cars as purely mechanical, these days the electrical system is more important than ever. A poorly functioning alternator, a weak battery, or faulty wiring can be the root cause of a number of problems. Before you blame the engine, pull out your voltmeter! Voltmeters show up in places you wouldn’t even expect! Jewelry stores typically have one on hand to measure the voltage in watch batteries. Next time you go to get a battery changed, ask them to bring it out and make sure that new battery really is new. Really, there are so many cases where a voltmeter could be useful that it’s impossible to list them all. If you don’t have one, or yours is starting to fall apart, get one right away. |
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Safety Precautions |
Part of knowing how to use a voltmeter is knowing how to be safe. You should always follow the best practices for working with electricity.
Turn Everything OffWhenever you are working with electricity, you should be sure that no electricity is flowing through the wires you are working on. Check your circuit breaker and see which circuit to disable before starting any work. If you have an older system that uses fuses, you can pull the fuse from the box and disconnect the circuit that way. As we said, use your voltmeter first to verify that the circuit is in fact disconnected. Nothing startles you more than an unexpected spark, and if you’re working on a ladder or a roof, those surprises can have deadly results. Of course, to measure voltage you are going to have to turn the power back on. However, you should leave the power off while you get situated. |
Be Careful What You TouchNever touch the bare metal of the probes when you’re measuring the voltage in a circuit. Doing so would connect you to the circuit, and you’re going to have a bad time. AC shocks can be lethal, so keep those fingers of yours on the insulated parts at all times! If your voltmeter has detachable probes, make sure that the red one is in fact plugged into the positive terminal on the device. Accidentally plugging these in incorrectly could cause problems, especially on older or cheaper voltmeters. |
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How to Use a Voltmeter |
Getting Ready |
First, make sure the voltmeter is ready to go. You’ll want to attach the probes if they’re not already hard-wired in. Then, make sure the voltmeter’s power source is in place and working properly. Once you have it put together, then it’s time to prepare for testing.
Before you start probing everything in sight, find a good place to set your voltmeter down. You’ll need both hands to place the probes, and for safety you shouldn’t just let the voltmeter hang freely in the air. Next, you should adjust the settings on the voltmeter to prepare it for the job you’re going to do. If you’re measuring the voltage in an AC circuit, set the voltmeter to AC Voltage (ACV on many models). In contrast, if you need to test a DC circuit, switch it to DCV.
Placing the Probes |
If you absolutely must measure the voltage in the middle of a wire’s run, then you’ll need a needle to poke through the wire’s insulation. Stick it in, and put the probe to that. Remember that the red probe should go the positive terminal on a battery. If you’re measuring ACV, then it doesn’t matter which probe goes where, since it’s bi-directional.
Once your positive probe is placed, put the negative probe on the negative terminal for batteries. If you’re measuring a single DC wire and don’t have a negative terminal, then put the black probe on a piece of grounded metal.
With both probes placed, the voltmeter should read the voltage passing through the current. If you see the number fluctuating, be sure your probes are steady and making good contact with the circuit. If the number still bounces around, then you may have an issue with the current flowing through the circuit.
Cleaning Up |
Once you’re done, remove the probes. If you used a needle to probe a wire, be sure to kill the power and take it back out. Cover the hole up with tape to prevent an unwanted short circuit.
Put your voltmeter back where it belongs, and close up any panels or replace covers.
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Conclusion |
So now you know how to use a voltmeter! Hopefully now you won’t be so squeamish around those pesky electric circuits. Even though it’s important to be cautious around electricity, a voltmeter will remove the guesswork from a lot of your jobs.
Getting rid of those doubts will make your work faster and more efficient. By knowing how to use your voltmeter, you’ll get more work done faster. It’s absolutely an indispensable piece of equipment for any do-it-yourselfer.
Once you start using your voltmeter, you’ll see just how easy it is. It’ll become second nature after an hour: but always remember to be careful when you work.
Featured Image Source: Pixabay.com
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