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How to Use a Non-Contact Voltage Tester

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A non-contact voltage tester is the safest way to make sure the power is off without touching any wires.

Before you open an electrical box, you should:
  - cut off power to the outlet at the main electrical panel
  - confirm you turned off the right circuit

This is where the non-contact voltage tester comes in handy.  The tester will light up and/or make noise when it comes close to a hot (live) wire, even one that's covered in plastic insulation.  Note that it can't test through metal conduit or metal sheathing.

Before using the tester, check its batteries the easy way: by shoving the tip into a live electrical socket, or holding it against the cord or bulb of a lit lamp.  You'll hear continuous chirps or see a series of flashes to confirm the tester has detected voltage. 

When testing a receptacle, just put the tip into the smaller (hot) plug slot.  Of course, it's always good to check the larger (neutral) slot in case the receptacle was mis-wired,  Make sure you've checked all slots in the receptacle in case they were wired differently or on different circuits, and if the receptacle is connected to a wall switch make sure the switch is on during testing.  After you unscrew the receptacle, pull it out and directly test all the wires again to confirm they're not live.  It's also a good idea to test any other wires reachable from the back of the receptacle.

When testing a power switch, unscrew and remove the cover plate then place the nose of the tester against the screw terminals on the side of the switch.  Once you confirm the wires aren't live, it's safe to unscrew the switch and continue testing other wires in the box.

When testing a light fixture, turn the circuit off at the main panel, and ensure the light switch is turned on.  Then unscrew the light bulb, and place the nose of the tester onto the center socket button.  If the light has two switches (on a three-way switch), test with one switch in both the up and down position.  Once you've confirmed the fixture isn't live, it's safe to unscrew it from the electrical box, pull it out, and test any other wires you see.

For more information on electrical projects check out The Family Handyman - Electrical

- By the DIY experts of The Family Handyman Magazine

spiderham10 months ago
If you're going to use one of these get a Klein. I've used the Greenlee, Ideal and Craftsman versions and all have given me false reads. I now have 2 Kleins, one at home and one at work, and neither has given me a false read.
Balord11 months ago
Hey! I discovered another use for these non-contact testers! In days gone by I have done (as I'm sure nearly any back yard mechanic has) the age old test for ignition spark by either putting a screwdriver in the spark plug socket and turning over the motor and check for visible spark....it does work and in fact an auto repair shop I frequent still does it this way. Or as a younger lad I have been known to do the grasp test on a lawnmower or go-cart plug (OUCH!). These testers make both of those obsolete! And they can be used in any of the situations mentioned by ONE person with ease! Faster too since no removal of plug wires needed. If you have no partner, simply (depending on the type) turn it on or in my case put a rubber band around the clip so force it to 'on' condition. and place it near a plug wire and then turn the engine over, my tester has an audible beep along with the light. Of course if too close to the starter wire and/or alternator my tester will also pick those up but continually whereas the plug wires are intermittent..
I am an electrical teacher at college (apprenticeships) and it is difficult to find anyone (respectable) who would recommend the use of these tools - or Death Sticks as they are commonly called.

Not only is it 'common' to get false positives but it is also common to get false negatives. I have had mine go off on a hot dry day in Australia by just having it in my tool bag - try rubbing one on your hair (or arm if your hairy like me). Static makes them trigger easily.

I own a Milwaukee death stick and I know I need to place it very specifically next to the active conductor in 2.5mm TPS (common 'flat' house cable). If I turn the volt stick more than 10 deg or so, there is no reaction. Granted other brands are not as sensitive as Milwaukee however ideally, decent death sticks can find one active cable in a bundle of 20 or more circuits easily.

As Binnie said - good 'first point of call' but should NEVER NEVER NEVER be used to determine if a circuit is de-energised or not. Take it from someone who has made the mistake and ended us seeing what 230Vac does to the jaws of a $70 pair of pliers at close range!

Hey Phil B, not sure where your from, but in Aus, I can go to any electrical wholesaler and get a cheap polarity tester for about $12 to $15 - 5 to 10 quid
binnie1 year ago
I would not rely on these non contact sticks, they are a good place to start checking if a circuit is dead, however they are not to be trusted!!
I don't think this instructable is really necessary. I t is well made though.
Ironically I just purchased one of these voltage testers for a home repair project. Up until now I was using the el-cheapo contact style with bulb but needed something to test over shielded wiring.

For some of us who are relatively novices and share a healthy respect for electricity, I appreciate the comments on the proper use of this tool. Too often the manufacturer will package a device without sufficient guidance, assuming a working knowledge.

For example, the author's comment around testing the neutral in case of mis-wiring, which can occasionally happen. Also liked the different use-case scenarios described.

I, for one, would love to see a sub-section on household tools (like a wiki) that describes use-cases, selection, care, alternatives and caveats.
Phil B1 year ago
I decided to purchase one of these after using one my daughter bought. I used it to get the polarity right when replacing the outlets in her house. It was very handy, especially since the old wires were coated in black rubber, not white and black plastic. When I looked at them in a store, there were several models in quite different price ranges. I learned the difference is the sensitivity to both high and low voltages. I chose one that would allow me to troubleshoot the low voltages along a string of Christmas mini-lights. I also noticed the less expensive units required relatively expensive button batteries, while the more expensive units accept regular common alkaline cells.
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