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Voltage tester, tick-tracer, glow-tip, non-contact voltage tester… whatever. Same thing. I call it a voltage sniffer, but the technical name for this device is a capacitive voltage sensor. That’s a term that I have never uttered aloud, btw. Voltage sniffers use black magic to determine whether or not wires are live, and they’re 100% reliable every time.
Ok, late April Fools. But seriously, I won’t try to explain how these things work because it’s above my pay grade. It has something to do with capacitive coupling, which the fabulously fine folks at Fluke were kind enough to explain in their three-page document, titled “Understanding capacitive voltage sensors“. If you want to know how they work, check out that document.
As a home inspector, I use my voltage sniffer for a few different things, and it’s important enough that I always keep a spare or two on hand. For a summary of this blog post in video format, check out the video below:
The most obvious use for a voltage sniffer is to alert you to live wires. I do this in attics more than anywhere else. I always check knob & tube wiring when I find it in an attic, because the first question anyone asks is always “was it live?”
Assuming you have a good, trustworthy device, it’ll do a good job of letting you know if a 120- or 240-volt circuit is live. Probably. These devices are not 100% accurate, but they do a pretty good job. You simply hold the tip near a suspected circuit, and it’ll tell you if there’s current or not. Probably.
I say “probably” because these devices are not 100% reliable. When a voltage sniffer lights up, it really means “maybe”. You can run a dead wire around a live wire, and the dead wire will set off the voltage sniffer because of the electrical field that’s placed on it. Do you remember creating an electromagnet with a wire, a battery, and a nail? It’s the same principle. The clip below demonstrates this perfectly.
That white wire isn’t connected to anything, but my sniffer is telling me it’s (possibly) energized.
Warnings: So what about the opposite of this? If a voltage sniffer doesn’t light up or beep at you when you’re holding it close to a wire, does this mean the wire is dead? No, certainly not. The wire might simply be connected to a switch that’s turned off. A wise home inspector would never report wires as ‘dead’ or disconnected unless they were able to completely trace the wires down and verify that the wires weren’t connected to anything at either end.
Also, manufacturers of voltage sniffers always recommend testing with a known source of electricity to verify proper functionality every time you use the tester. They also recommend holding the tester with your bare hand and keeping it close to your body. There may be some conditions where a voltage sniffer will fail to detect current if you’re not actually holding the device, as shown in the clip below.
Also, voltage sniffers cannot find live wires inside of properly grounded metal conduit.
Another use for a voltage sniffer is to locate ungrounded metallic fixtures. We routinely use voltage sniffers around metallic lights near kitchen and bathroom sinks to verify that the lights are properly grounded. If a metallic light fixture isn’t grounded and a hot wire was to come into contact with the fixture, it would silently energize all of the metal, making this an electrocution hazard. If we hold a voltage sniffer up to an ungrounded metallic light, it’ll light up. Once we touch the light, we change the capacitance and the sniffer shuts off.
This is probably what I use my sniffer for more than anything else. Not all metallic lights have to be grounded, however. The desk lamp pictured above is a good example of a light that doesn’t need to be grounded. If it were grounded, it wouldn’t set off my tester.
I’ve used many different voltage sniffers over the years and been frustrated with most. Voltage sniffers typically measure down to 50 volts, which means that a lot of low-voltage stuff will set off the tester. Even my 5-volt mobile phone charger was able to make a few of my testers go off.
To help reduce the potential for false positives from low voltage stuff, I recommend home inspectors use a voltage tester that starts at 90 volts. Fluke makes a couple of such testers, both the 1AC-A II and the 2AC. I prefer the 2AC because there’s no on/off switch. It’s always on, and a pair of AAA batteries will last a year or two. Also, the fact that it runs on AAA batteries is huge. I wouldn’t buy another voltage sniffer that runs on button batteries, because they’re harder to find.
I’ve had the Fluke AC2 for about three years now, and it has been the most reliable, rugged non-contact electrical tester I’ve owned. It costs a little more than most other voltage sniffers, but it’s definitely worth the price.
Author: Reuben Saltzman, Structure Tech Home Inspections
Those undertaking electrical projects around the home need certain tool box essentials at the ready, including a voltage tester. We recently put some of the best voltage testers through a series of hands-on tasks to select eight models that can speed up workflow and help keep you safe from shocks.
Voltage testers allow users to check for power quickly, easily, and safely. With plenty of different types of voltage testers from which to choose, consumers can benefit from knowing what to look for in a voltage tester and how to determine which is best suited to their needs. We performed hands-on testing in situations DIYers are likely to encounter and consulted a virtual electrical expert from Frontdoor.com for their professional opinion on using the tools to arrive at this list of top voltage testers by category.
We wanted to ensure that we were suggesting only the best voltage testers, so we did our homework. We performed extensive product research to collect some of the best models on the market and then performed hands-on testing to put them through their paces.
Plus, we consulted Chris Lozano, a master electrician with more than 10 years of experience at Rev Electric who now works at Frontdoor for his professional advice on these tools. He says that a voltage tester needs to be rated for the voltage that you will be testing. “A residential household uses a 120/240-volt AC system, so a tester needs to be rated up to 250 volts AC.”
Based on this advice, our initial tests included trying each model on outlets around the house, as well as testing appliance wires, including those that were plugged in and those that weren’t. We used each model to test a 240 volt (V) dryer outlet (except the plug-in model, of course) to ensure reliability and effectiveness.
Then, we checked each model for fit in a tool bag and shirt pocket, ensuring they were compact and easy to transport.We even measured each model to include an accurate depiction of their size in our product specs, not the packaging dimensions most sites provide. Models with extra features (like a thermometer, flashlight, and other settings on the multimeter) were also tested accordingly to see if those bells and whistles performed as promised.
To ensure that the products on our list of top picks included the best features available and were safe to use, we consulted Terry Dussault, a safety expert and the CEO of Yellowknife Consulting Services in Huntington Beach, California, who has more than 25 years of experience working with products such as these. It is Dussault’s belief that testers should have “noncontact voltage detection, audible alerts, and a broad voltage range, which can streamline the testing process and enhance productivity.” Dussault also pointed out that a tester should be “certified by a recognized safety organization, such as Underwriters Laboratories or Conformité Européenne.”
Models that passed all of these tests were given awards based on their strengths. Those that failed the tests were discarded from the list. The result was this lineup of the best voltage testers.
Below, DIYers will find details about some of the best voltage testers on the market—all from trusted brands that produce quality electrical tools, and all of which have been put through their paces with our hands-on testing.
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Photo: amazon.com
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The Fluke 1AC II noncontact voltage tester is a quality pen tester from a leader in the electrical testing industry. This tester can detect voltage between 90V and 1,000V while fitting comfortably in a tool pouch or a pocket. When it detects voltage, the tip glows bright red as an alert.
The Fluke 1AC II voltage tester features a continuous self-test indicator that flashes red to alert that it’s working. It also has a loud, audible beep to indicate it is detecting power, but there is a disable function for quiet environments. This Fluke voltage tester runs on two included AAA batteries, and it features an automatic shutoff to save battery life.
We found that this voltage tester was extremely easy to use. The self-testing indicator is a handy feature, as it constantly alerts users that the tool is in fact working. We noted it also alerts to power quickly when it is turned on (some models take a few seconds). It fits well in the tool bag, and the sturdy clip locks on easily. Turning it on with or without the beep (it depends on how long the button is held down) took some getting used to, but it didn’t impact the tester’s functionality.
Get the Fluke VoltAlert voltage tester at Amazon, Lowe’s, or Walmart.
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Klein Tools produces top-notch tools for electrical professionals, and the Klein Tools NCVT-1 noncontact voltage tester lives up to the company’s legacy. It can test for voltage between 50 and 1,000V of alternating current, and it fits nicely in a pocket or pouch.
The NCVT-1 voltage tester uses an easy-to-understand red-and-green indicator to alert the user to power: green for no power and red for voltage. It also beeps steadily when it detects voltage. It features an automatic shutoff to stretch battery life and a low-battery indicator that alerts when the included AAA batteries are about to run out.
While it might drain batteries a bit faster than some other voltage testers, the constant green this tester emits when it’s on proved to be a nice touch during testing. It not only indicated that the model was working but slightly illuminated dark spaces, too. We also like that this tester is compact, measuring just 5.5 inches long, making it more than suitable for a tool box or bag. Also, the automatic shutoff turns off without a loud beep, saving energy and avoiding startling the user when working with an electrical device. Our only complaint is that while the tail cap that retains the batteries is secure, there are gaps around the cap that prevent it from sealing completely.
Get the Klein Tools NCVT-1 voltage tester at Amazon, The Home Depot, or Acme Tools.
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For a reliable, value-minded voltage tester, the STK001 noncontact voltage tester from Sperry Instruments is worth a look. This pen tester comes with a plug-in outlet tester, allowing users to test wires and outlets with one kit.
The pen tester detects voltages between 50 and 1,000V. When it detects voltage, it will beep loudly, and a clear plastic that houses the bulb will flash red. It runs on one AAA battery (included), and it has a low-battery indicator to ensure it’s working. The outlet tester will alert the user to voltage as well as open grounds, open neutrals, open hots, and reversed polarities. It can also test ground-fault circuit interrupter (GFCI) outlets to ensure they’re working properly.
Our assessment of the Sperry kit is that it offers a lot of value for its price point. For a relatively low cost, consumers get two tools to detect voltage. The plug-in tester proved easy to use, and our testing of outlet wiring configurations was a breeze. Also, tripping GFCI outlets was simple, requiring just the press of a button. We found that the pen tester is extremely sensitive and occasionally alerts to voltage that isn’t present, but at least it errs on the side of caution.
Get the Sperry Instruments voltage tester at Amazon, The Home Depot, or Walmart.
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Often, electrical professionals need a fast way to test a wire and take a measurement without finding a junction or outlet. The Fluke T6-1000 Pro electrical tester multimeter’s Field Sense setting detects voltage, plus it measures the voltage without disconnecting connections. Simply slide the testing fork over the wire, and the T6-1000 will report on the wire’s condition.
The T6-1000 features all the other common settings expected from a multimeter, including both DC and AC, amperage, and resistance measurements. This durable voltage tester comes with alligator clips, swappable test leads, and a holster to keep it close at hand.
As a multimeter, the T6-1000 worked just as we expected it to, providing readings on voltage, resistance, and amperage as well as hertz (helpful for electrical motor service and other equipment). The fact that it can indicate the presence of voltage between the forks is a nice benefit, allowing it to serve as a noncontact tester as well as a standard multimeter. However, in our experience, the actual voltage readings weren’t nearly as accurate as those of the regular leads. For user convenience, it comes with a holster, swappable leads, and alligator clips for easy transport.
Get the Fluke T6-1000 voltage tester at Amazon.
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For electrical work around equipment that runs a bit hot, such as boilers, furnaces, and industrial equipment, the NCVT-4IR voltage tester from Klein Tools is a smart choice. In addition to detecting voltages within a range of 12 to 1,000V, this model features a built-in infrared thermometer. The thermometer can detect temperatures between -22 and 482 degrees Fahrenheit, providing safe, hands-free temperature checks.
The pen tester features a two-color LED system: blue to indicate that it’s workingand red when it detects voltage. The infrared thermometer has a built-in laser pointer that makes precise measurements easier to achieve. Both functions run on two AAA batteries, and there’s a built-in shutoff to preserve their life.
While the NCVT-4IR pen tester—an infrared thermometer and noncontact tester in one tool—is designed for HVAC mechanics and technicians, DIYers ought to appreciate it as well. In testing, the laser was easy to use, though slightly weaker than we would’ve liked. This model had the best range, though, detecting lower voltages than the others tested. It is fairly bulky compared to other pen-size models, but that bulk might be considered a benefit, since this model is resistant to dust and water penetration and proved unaffected by either during our test.
Get the Klein Tools NCVT-4IR voltage tester at Amazon, The Home Depot, or Walmart.
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Folks who want to ensure they can see exactly where and what they are testing will want to consider Greenlee’s noncontact voltage detector. This model has a built-in flashlight that the user can turn on when needed to see into dark corners or spaces.
This model can detect voltage between 50 and 1,000V AC. In normal powered-on mode, it flashes red to indicate that it’s working. Upon detecting voltage, the red LED flashes rapidly and the model beeps, indicating that there is power present. The automatic shutoff turns the pen tester off after 5 minutes of inactivity, and with its rubberized grip, holding onto it is a bit easier to manage.
We found quite a bit to like about the Greenlee during testing. First, the rubberized texture makes holding this model comfortable and less likely to slip. Also, the flashlight illuminates darker spaces enough to find the wires, outlet, or device that needs testing. We particularly liked the size, since it’s one of the most slender models going and fits well in a shirt pocket or tool bag. We would prefer that the LED light change color upon detecting voltage, but the rapid flash and beep work well.
Get the Greenlee voltage tester at Amazon or Grainger.
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Whether it’s a spare to toss in a tool bag or the main voltage tester a technician keeps in a shirt pocket, the Ideal Industries 40-1000V AV Volt Aware NCVT is a worthy choice. This model isn’t much larger than a typical magic marker, so it fits easily within most clothing pockets and can even slip into a pencil pocket in a tool bag or tool belt.
This tester can detect voltage between 40 and 1,000V AC. It has a green steady light that indicates when it’s onas well as a red flashing light and beep that indicates when it detects electricity. The rubberized body prevents slipping out of the hand, and the silence/beep toggle button near the tip is easy to access and use.
We found it super handy to tote this tester in either a shirt pocket or the one on our tool belt because it’s not just compact, but also rounded, taking up less space than a square-cornered model. We also liked the twist-on and twist-off function for a more tactile response than pressing a standard on/off switch, and the rubber grip makes grabbing it out of a pocket a breeze. The pocket clip is pretty flimsy, however, so should it break off, the cylindrical tester might easily roll off a table or shelf.
Get the Ideal Industries voltage tester at Amazon.
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Photo: amazon.com
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While most pen testers will clip to a pants pocket or fit inside a shirt pocket, bulky models won’t feel comfortable to carry that way. Enter the 2AC noncontact voltage tester from Fluke. This pen tester measures just 5.75 inches long and 0.75 inch in diameter, so it can slide into a pocket with ease. It also weighs just 10.6 ounces, so it won’t feel heavy when clipped to a shirt.
The Fluke 2AC voltage tester detects voltages between 90 and 1,000V, and it glows red to indicate that it detects voltage. However, while the product description claims that the tester also beeps upon voltage detection, the model we used did not (some online consumers had the same complaint). The lack of an audible beep was somewhat of a letdown, as all the other models tested have that capability. But this model doesn’t have an on/off switch, which means it’s always in “on” mode for easy use. And since there’s a built-in battery indicator and automatic shutoff, it should not drain its two AAA batteries.
Get the Fluke 2AC voltage tester at Amazon or Walmart.
Here are the most important factors to keep in mind when choosing a voltage tester, including designs and functions.
There are three basic voltage tester designs: pen testers, outlet testers, and multimeters.
In general, voltage testers are only useful for checking for alternating currents, such as the electricity in a dwelling or commercial building. They don’t help detect the direct current in a vehicle.
But that doesn’t mean that all voltage testers are one-trick ponies. Some pen testers have built-in features like flashlights, measuring lasers, and infrared thermometers. Many outlet testers can alert the user if the outlet’s wiring is backward. Multimeters can test for AC and DC voltage as well as resistance, amperage, and more.
Each user’s individual needs will determine which functions are necessary for a voltage detector. To simply test a wire for power, a pen tester can do the trick without confusing buttons or switches. If tackling a variety of electrical projects, a multimeter might be a real asset.
For those who are new to these tools, Lozano says that one of the best ways to get the hang of using a voltage tester is the “live-dead-live” test, which can ensure the testing equipment is working. “Take the meter to something you know is working to test if it is live, then turn it off to test if it detects it is dead,” he says. Finally, test it again on the live part. “That will tell you if the testers are working and if the meter is in the right setting.”
Voltage testers aren’t compatible with every electrical device a DIYer might come across. Certain types of voltage, or voltages outside of the range the tester can detect, won’t cause the tester to alert.
Pen and outlet testers are excellent for testing electricity within the home, including switches, outlets, and fixtures, but they’re typically useless when it comes to checking for issues with a vehicle’s electrical system. Many pen testers also have voltage working ranges—such as 90 to 1,000V—so some may not be able to detect low voltages.
If taking on electronic device repairs (computers, drones, or televisions, for example) or working on a vehicle, look for a multimeter with a built-in voltage tester. A multimeter can switch between alternating and direct current as well as test for resistance and amperage. An HVAC multimeter can check fuses, switches, and other components of an HVAC system.
For long-term use and durability, choose a voltage tester from one of the trusted manufacturers in the electrical tools industry. These companies specialize in creating electrical tools for pros, and their products are top-notch—many pros still use meters and testers they purchased decades ago.
Battery life is also a consideration. Many of the best voltage testers have automatic shut-off functions. If they don’t detect voltage within a certain amount of time (usually around 15 minutes), the tester will automatically shut off to prolong battery life.
Those who still have some questions about choosing or using the best voltage tester will want to consider the answers to some of the most frequently asked questions about these tool kit essentials. Find more vital info here to make an informed purchase.
No, voltage testers and multimeters are not the same, though some multimeters feature voltage testers. Voltage testers indicate only the presence of voltage. Multimeters can test the amount of voltage, amperage, or resistance in a fixture or circuit.
Yes, voltage testers are safety tools, and they’re safe to use. They have insulation to protect against current transfer so the tester can’t transfer electricity to the user’s body.
Most voltage testers feature battery indicators that automatically alert you to advise that the tester is working. Others might require you to activate the battery test. If you’re unsure, check an outlet you know is working to ensure the tester is functioning.
Bob Vila has been America’s Handyman since 1979. As the host of beloved and groundbreaking TV series including “This Old House” and “Bob Vila’s Home Again,” he popularized and became synonymous with “do-it-yourself” home improvement.
Over the course of his decades-long career, Bob Vila has helped millions of people build, renovate, repair, and live better each day—a tradition that continues today with expert yet accessible home advice. The Bob Vila team distills need-to-know information into project tutorials, maintenance guides, tool 101s, and more. These home and garden experts then thoroughly research, vet, and recommend products that support homeowners, renters, DIYers, and professionals in their to-do lists.
Tom Scalisi is a full-time DIY and construction writer for many of the largest websites in the industry, including BobVila.com, This Old House, Family Handyman, and Forbes. He also owns and operates a pest control blog, RiddaBugs.com.
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