Non Contact Voltage Testers

Voltage Testing. When you do it for Contact Purposes (Physical Touching or Application of Tools or Connections to a Point that is capable of being Electrically Energized), it must be done Very Carefully. If you make a Mistake, it could cost you your life, damage equipment, or both, and the use of a Multimeter or Tester connected by Leads to the desired point is the Standard Test (in voltages commonly seen at home) to Verify that the Point is De-Energized. But at times, it’s handy to know if something is Energized (hot) or De-energized, and Non-Contact Inductive Voltage Testers Can Help.

Below this point, I shall refer to an Inductive Voltage Tester as a Non-Contact Tester and a Multimeter or Voltage Tester that requires Physical Connection to the desired point as a Tester.

Christmas Vacation Lights Scene 

If Clark in Christmas Vacation had a Non-Contact Tester, he would not have had the Connection Anxiety that he did. Yes, he could have used a Simple Receptacle Tester, or a Tester Connected to the Circuit, but there was no need to do that. Since he just needed to know if it’s Energized or not, the Non-Contact Tester would work.

A Word About Receptacle Testers

A Word About Receptacle Testers

Testing Christmas Lights, when you know the procedure, is something that Non Contact Testers can be used for. Incandescent Twinkle Lights are Wired In Series, and so are Christmas LED Light Strings. If you’re old enough, you may remember C6 Incandescent Bulbs. We had Candelabras that used 8 of them. With 120 Volts (in the U.S. and similar areas), 120/8=15 so the C6 Bulb was actually a 15 Volt Bulb. They were wired in Series, so that 120 Volt was across the total String, and each Bulb saw 15 Volts.

But when one burned out, they all went out. We used to take a known good bulb and swap a bulb, one by one, until the Candelabra Lit and we knew we had the Bad Bulb. Then, I test the Bad Bulb in another Candelabra to be sure it was bad.

The Series/Parallel Light Configurations can be seen on my Blog at the Following Link:

Christmas Lights Basics and Inspections

Christmas Lights Basics and Inspections

C7 Bulbs were introduced, and they are rated for 120 Volts, and the bulbs were in parallel, so as a Bulb Burned Out, the remainder stayed Lit.

The Twinkle Bulbs used a Shunt at the base of the Filament Stands, and if the Filament Burned Out, the Bulb went out, but the String Remained Lit. If you pulled the Bulb, all the lights on the String Went Out. Sometimes the Shunt was missing, sometimes it wasn’t making contact, and the String Went Out. Using a Non-Contact Tester, you can find the offending Bulb.

Though the following makes it look simple, it takes practice, and with time, the Non-Contact Tester can be useful.

Fix LED Christmas Lights with One of These in a Few Minutes

There are many models of these Inductive Testers. I’ll link to Videos about them. There are many Limitations, use them carefully.

Wet Romex. Shazzam, I never knew this, but if the Romex Paper is Wet, it blocks the Non-Contact Tester from working:

Comparing popular NCVT’s on Wet Romex”

Below, this includes the Fluke LVD1, a different Lighted Fluke version available, and others:

The Non-Contact Sensor Tip Shield is Broken-Off one of the Non-Contact Testers in this Video, DO NOT USE THESE WITH THE METAL SENSOR TIP EXPOSED, have it repaired or purchase a new Non-Contact Tester.

Fluke VoltAlert: 1AC-A II VS 2AC VS LVD1 VS LVD2

And Different Manufacturer and Model of a Lighted Non-Contact Tester:

Klein New NCVT-3P Dual Range Non-Contact Voltage Tester with Flashlight


Remember, Non-Contact Testers are not to be used to determine if something is Electrically Energized if the purpose is to Touch the potentially energized point, or to work on the Potentially Energized Point via the Application of Tools or to Make or Remove Connections from the Energized Point. There is too much chance that harm will result. A Multimeter or Electrical Tester that uses Test Leads and assesses the Potential (Voltage) from one point in Reference to Neutral and Ground must be used.

While writing this Blog, and using 2 of the models I discuss, the Refrigerator, Stove, and Microwave show that the shell of the appliances is not Energized. That’s a Good Thing. Yet the Fluke LVD1 shows the proximity of Voltage on the Freezer and Refrigerator Doors, but this may be why:

“Your refrigerator is hot on the door seal because of a Heater around the freezer and refrigerator compartments that used to prevent condensation. If the door seal was not heated, the cold air would encounter the warm air outside of the fridge, causing condensation to form.”

So, Technically, the Heater is Inside the Refrigerator, not Inside the Doors, but there is a source of voltage near the Door Edge.

Edification on the Nature of the Heaters, For Older Refrigerators and Energy Efficient Ones:

I Feel Heat/Warmth on the Front Edge of my Refrigerator….Why?

Several years ago, preparing to move into my current Home, we realized the Wiring needed to be Modernized (which we had done before moving in). Many of the Receptacles had no Grounds. It seems the House was wired with Knob and Tube, and a few more modern circuits had been added to allow the use of Window AC Units or for other purposes.

I’m not sure why I tested it, but in the process of preparing the house for us to move in, and while Re-Wiring of the house was ongoing, I took a Non-Contact Tester (the yellow one on this Blog) and held it to the shell of the Refrigerator. It lit up, and made the associated sound, very aggressively. Something was wrong.

1. The Receptacle wasn’t grounded. The purpose of Grounding the Shell of an Appliance is in case an Electrical Insulator Fails (insulation worn through), Component Failure that Grounds the component to the body of the refrigerator, etc. Sometimes a wire in the Fan or Compressor shorts to its Shell, and the Case of the Refrigerator become Energized, and in this example, the Voltage may be reduced from the Source Voltage, it would not be uncommon to see 60 Volts from an Ungrounded Refrigerator Shell to Ground on a 120 Volt System. If the Shell of the Appliance is Grounded, No voltage will be seen and if the short is serious enough, the Breaker will Trip in the Main Panel. If the Shell is not Grounded, the Shell of the Appliance can become Electrically Energized.

2. Rats, we had Rats, in the House (we had not moved-in yet), it gives me the creeps. $800+ Dollars Later, and monthly payments for “Inspections” for the next year, and the issue was resolved. See the Power Cord for our Refrigerator. Most people won’t have Rats, some may have Mice, some may have Pets, and some may not have any living thing chewing on the cord, but abrasion, vibration, inferior insulation quality, and the like can cause a similar effect in terms of the shell of an appliance becoming Electrically Energized if the Ground is not Intact.

Chewed Cord 001 - 1

Chewed Cord 002

Rats and Wires 2

Had we touched the Refrigerator and the Sink, or Stove (if the Stove was Grounded), it’s possible Electrocution could have resulted. Investigation of the Refrigerator showed the Power Cord with strands hanging out, and they were touching the metal parts of the refrigerator, and they were making the Shell of the Refrigerator Electrically Hot. Replacing the Power Cord restored the safe operation of the Refrigerator, and the Rewiring of the Receptacle Restored the Ground and it will prevent the Dangerous Condition of an Energized Shell on the Refrigerator. The Receptacle being Ungrounded was probably the reason that the Rat, in the Refrigerator Frame (behind it, underneath) was able to expose the Bare Wires without being Electrocuted. Had the Refrigerator Shell been Grounded, the Rat would have been shocked, and possibly killed, the first time he contacted the Wire.

I have the Following Non-Contact Testers:


1. Fluke Volt Light Model LVD1 (White LED Work Light and Blue/Red Energized Circuit LED – as seen to the Left of the Green On/Off Switch). Uses 1 AAA Battery.

2. Greenlee Model 1010 (Red Energized Circuit LED and Tone Buzzer). Uses 2 Button Batteries.

3. Greenlee Model GT-11 (Red Energized Circuit LED and Tone Buzzer). I added the Purple Electrical Tape, the Pocket Clip Broke and it holds it in place. Uses 2 AAA Batteries.

In terms of practicality, i.e. using it in Industry, I would say that the items 2 and 3 above are the better choice (of the 3), or similar products by reputable companies. But around the house, item 1 is noteworthy. I began this Blog Entry because I use the Fluke Volt Light as a Light, though not exceptional in a small light, it’s especially handy to Clip-On a Pocket, or Near a Point of Work, and focus the Beam on the desired work area. Since it has an Inductive Voltage Tester in it, it can be used (see limitations of such devices, way above) to see if a Wire, Extension Cord, Power Strip is Energized.

I am an Advocate of Power Strips with Simple On/Off Switches, and Fuse or Breaker Protection, to plug the ever present Cellphone and Computer Tablet Transformers into. The reason that I support their use for these items is that they can be turned-off at Bed-Time, Precluding a Failure in the Transformer that could cause a Fire. We have 3 Power Strips in the Living Room that we turn-off at Night.

Power Strips, Information on Use and Safety

Power Strips, Information on Use and Safety

The Power Strip next to me has 6 Transformers Plugged-into it, and all three Non-Contact Testers Flash the Energized Light, and Items 2 and 3 make the sound; characteristic of an Energized Circuit; just approaching the Strip with the Non-Contact Testers. Of course, if the Power Strip was not Plugged-in, none of them would make noise or light-up.

I tried another Power Strip, it has a Metal Shell (by far the best to get if possible) and no Transformers Plugged-in. Item’s 2 and 3 were properly Sensitive, as the Slight Protuberance (sorry, I don’t have use for that word often, a Slight Projection) accurately showed which of the 2 Receptacle Openings was Energized [In the U.S. the Neutral is the Wider Opening, and the Hot (Energized) is the Smaller opening (this is for use with Polarized Plugs)]. The Fluke Volt Light showed Energized, but I was not able to Isolate which of the openings were energized or not.

Onto the Kitchen. A wall Receptacle near the Sink. As usual, Items 2 and 3 worked fine, and showed the Neutral and Energized Openings correctly. With Practice, I was able to locate the Energized Opening with the Fluke Volt Light, but not as a Cleanly Not-Energized / Energized Reading that Items 2 and 3 did with their Projecting End, but as a Blue LED over the Neutral Opening, Changing to a Red LED when held “Just Right” over the Energized Opening. The Fluke Volt Light Shows Blue when approaching the Source Voltage, and the same LED Turns Red when Closest to the Source Voltage (providing you can get Close Enough).

Last, testing the Power Cord to the Table Light next to where I am sitting:

1. My house has been rewired by a Residential Electrician, and each Receptacle Tested for Correct Wiring by a neurotic man – i.e. myself.

2. In the U.S., SPT-1 was what older simple household Extension and Table Light Power Cords used. The Insulation was relatively thin. More Robust Cords known as SPT-2 are now used, they have thicker Insulation, and often Stress Relieved Plugs. SPT-2 Wire may not Fit up through the Tube in Lamps that take the Wiring from the Base to the Socket, and if so, SPT-1 Replacement Cords are still available.

“What is the Difference Between SPT-1 and SPT-2 Wire?

In a nutshell, the difference between SPT-1 and SPT-2 is the thickness of the insulation. SPT-1 is .03″ and SPT-2 is .045″”.

If the Receptacle is Wired Correctly, and if the Plug is Correctly Connected to the Cord, in the U.S., the Ribbed Insulation (may be multiple Ribs or just 1 or 2) should be connected to the Neutral. If a Variation in Marking Exists, examine the Plug, on Simple 2 Wire Cords, the side with the Wide Prong (on Polarized Plugs) goes to the Neutral Wire, and you can see if Ribbing or Writing is Exclusively Used on the Same Side as the Neutral Prong.

One Purpose of Polarized wiring is to Connect the Neutral to the Socket (Threaded Area) of the Light (and would not be energized) and the Energized Wire is connected to a Switch and then to the Center of the Base of the Light Bulb (Incandescent, Fluorescent, or LED) to reduce the chance of someone being shocked when Changing the Bulb. Sorry for the lengthy explanations, but people should understand how and why things are as they are.

Using the Non-Contact Testers, Items 2 and 3 easily show the Neutral (Ribbed) and the Energized Wire (writing on the Insulation in my example). The Fluke Volt Light LVD1 requires more care when holding the end of the Non-Contact Tester to the points being tested. Even on the Neutral, the Blue aspect of the LED is Lit, meaning that voltage is nearby. When holding it at the Energized Side of the Cord, the Red LED is clearly Lit. But the End of the Fluke Non-Contact Tester needs to be Held Against the Far Edges of the Wires to produce the Blue LED (on the Neutral Side) and Red LED (on the Energized Side). Items 2 and 3 were more tolerant with not being at the very Edge of the wire, and showing the Neutral (no Light or Sound) and Energized (Red LED and Sound) sides.

Holding Fluke for Measurement

A Side Note Concerning Cellphone and Table Charging Cables:

All three of the Non-Contact Testers show that the Device End Plug of the Charging Cable is Energized when the Transformer is Plugged-in and the Cable Connected to the Device. The Fluke LVD1 and the Greenlee GT-11 Show the Cable to be Energized in this example, but the Greenlee 1010 only shows the Cable to be Energized in Spots, Likely due to the Twist of the Conductors in the Cable and increased distance from the Tester Projection in areas.

The Fluke Volt Light LVD1 and Greenlee GT-11 Shows the Connector and Charging Cable to be Energized if the Transformer is Still Plugged-in with the Charging Cable Disconnected from the Device.  The Greenlee Model 1010 only worked if the Projecting End was Carefully Held Flat Against the Broad Sides of the Device End Connector and Moved Around to find the Sweet Spot, and the Cable tests as Energized by the Greenlee 1010 at times, but not at other times.

Anyway, these Devices may offer the user the ability to see if the Low Voltage Device is Plugged-in, but as they are not designed to work with Low Voltages, it would be a Trial and Error thing. But if I felt confident with a Specific Model and knew how to apply it to see if the Device Connector End or Cord was Energized or not, I’d use it.

Testing Computer Cables

There is, in the case of USB Devices a better idea, it’s not expensive, mine came as Shown Below and included a USB Resistor Pack (not shown) to plug into the Meter to simulate a Load to see if the Voltage Remained sufficiently high to charge the device. The Resistor Pack is just used briefly, it can be too much of a load for the Transformer and it becomes Hot Quickly. Using Converters to go from one USB Connector Style to Another, a Variety of things can be Tested using this Meter.

USB Tester

Non-Contact Voltage Testers have valuable uses. They can locate a broken energized wire in a cord, can help confirm something is Energized that you expect to be Energized, but should not be used to prove something is De-Energized if you intend to touch the conductor, apply tools, add or remove connections, etc. There are instances when these testers will show something De-Energized when it’s actually Energized, and instances where they show something as Energized that is actually De-Energized.

I have used these on the shell of appliances and had it showed Energized, and additional checking with a Tester proved that to be correct.

The Fluke, with the Work Light, is very convenient, I use mine mainly for the Light, but the Tester Built in, it’s easy to Experiment and see what Activates the Blue Light (Nearby Electromagnetic Fields), and as such, I can see the way the Power Strip is next to my Couch, it may be better to move it, as to the Fluke, the Entire Area represents a Nearby Energized Field. I suspect that the Body works as an Antenna for it, and it’s showing Blue (Nearby Fields) that should be a concern to those with an Awareness or Concern of Electromagnetic Radiation Sickness.

The Parts

In strictly Electrical Terms, the Greenlee Non-Contact Testers are likely better for Locating the Hot and Neutral Side of Receptacles and Cords, reaching-in to determine if a Wire in a Electrical Work Box is Energized, etc. (though do not Rely on it to Prove that the Wire is De-Energized).

Greenlee seems to have realized that the Work Light concept of the Fluke Volt Light Model LVD1 is a desired feature, as they too are manufacturing Lighted Non-Contact Testers. Though I would gladly own one of these other Lighted Non-Contact Testers, the Fluke is more adaptable to various circumstances, I wear it on my Pocket, and Aim it Out Front, it can be Aimed Down for Reading, Mounted in a Work Area for needed Light, and is a Non-Contact Voltage Tester as well.

Spec Sheet:

Fluke LVD1 Non-contact AC Voltage Detector and LED Flashlight (and Clip)

  • Bright white flashlight illuminates working area
  • Blue indicates you are close to ac voltage
  • Red indicates you’re at the source
  • Detects voltages from 40 V ac to 300 V ac
  • Comes with versatile clip to secure light to a pocket, hat or even a panel door
  • Operating Temperature 0 °C to 50 °C
  • Ultra-bright white LED with 100,000 hour bulb
  • AAA battery included

The Current Fluke LVD1 has complied with a European Standard on reducing Specific Electronic Waste and is now sold as the LVD1A, same appearance.

LVD1A RoHS Compliant VOLT LIGHT LVD1A is the RoHS (Restriction of Hazardous Substance) compliant replacement to the LVD1. 

I attempted to find the Data Sheets for the Greenlee Model 1010 and GT-11, but they are older models, if I find them, I will place the information here.

The purpose of this Blog is to Introduce Readers to the Concept of Non-Contact Voltage Testers, Point out Safety Concerns, Limitations, etc., to Convey the apparent Usefulness for Checking to see if Cellphone or Tablet Charging Cords are Energized, Repairing Christmas Lights, Finding Opens in Extension Cords, and much more.

I think the Flashlight Makes the Fluke very useful, as would a similar feature offered by other manufacturers. The Fluke LVD1 appears to be VERY Sensitive, and may be of some use to people that have Awareness or Concern of Electromagnetic Radiation Sickness to Show Nearby Electrical Fields. Hopefully the LVD1A is just as Sensitive. I purchased the LVD1A prior to writing this, but they sent the LVD1 (which I already own), so I won’t be able to compare.

Author: Dr-Artaud

A Doctor that is not a Doctor, but named after a character in the movie "No Such Thing", as is the Avatar.

One thought on “Non Contact Voltage Testers”

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