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22 of 22 people found the following review helpful
5.0 out of 5 stars one of the better adjustable noncontact voltage detectors
This is a wonderful device! A single adjustable unit can play the role of multiple fixed non-contact detectors and more, if used properly. Here are some interesting applications I've already put the GT16 to work on most of which cannot be done with a fixed detector.

Early detection of electric fields

Unlike fixed models that work best at a set...
Published on August 13, 2011 by James Q. Smith

versus
22 of 22 people found the following review helpful
1.0 out of 5 stars DO NOT TRUST THIS TESTER
Bought one of these to replace an old Greenlee I had for years. One of the really nice small round yellow ones. I loved the old one so I bought a new Greenlee. Had it for a week, and one day I tested a set of 3 wires for 480v. Checked the wires and read nothing. Checked a 110v outlet and it read voltage. Checked the 480, nothing. Looked at the bus bar and saw the...
Published on June 16, 2012 by Ro12


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22 of 22 people found the following review helpful
5.0 out of 5 stars one of the better adjustable noncontact voltage detectors, August 13, 2011
This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
This is a wonderful device! A single adjustable unit can play the role of multiple fixed non-contact detectors and more, if used properly. Here are some interesting applications I've already put the GT16 to work on most of which cannot be done with a fixed detector.

Early detection of electric fields

Unlike fixed models that work best at a set distance, you can use adjustable detectors to find potentially dangerous conductors behind covers such as plastic, rugs, thin walls, dry wall etc., it depends on the thickness and if the wiring isn't shielded by protective conduit. If the unit doesn't ring at its maximum sensitivity, then there is probably enough distance or insulation between those sources and you to reduce risk of an electric shock. The extra sensitivity thus, gives you a larger margin of safety by keeping you farther from those AC sources. Even if the field detected is not coming from mains AC, a field strength of a magnitude enough to turn on the GT16 has a potential for injury, so you are already alerted to proceed with added caution.

Feel a wire underneath a rug, not sure what it does? Before you even pull the rug open you have an idea what's there. You see exposed wires or extension cords all over at a job site, a basement or a backyard, that disappear into 'no where' or hanging all over the place, are they live or not? You can tell even without touching your detector to any wire, I've already tested the GT16 to alarm as far as 3' from an extension cord and 1' away when covered by 2 layers of rugs.

Isolating an unknown electric field

Using the GT16, sweep an area in arcs like with a metal detector, when the GT16 beeps, reduce the sensitivity slightly, move forward and sweep until it beeps again, keep repeating the sequence, you'll finally hit the AC source.

Estimating distance of a field using dial positions

Set at its lowest sensitivity setting, the GT16 detect mains voltage only when the nose is inserted into a known live and proper electrical socket. The GT16 alarms continuously inserted into the HOT or shortest socket, not when at the NEUTRAL or long socket or the GROUND or round socket.

With the lowest sensitivity now known, test the GT16 on an extension cord plugged into the socket. The GT16 detects the hot and neutral lines of the cord just like a fixed voltage detector: you need to touch that part of the cable with the nose of the GT16 for it to alarm.

Slowly pull away from the cord until the GT16 ceases to alarm, then adjust the sensitivity up until the alarm restarts. Note the distances and number of turns; I use my hand and finger widths as a ruler. For available cords I have around, I consistently get about 1-3'.

You now have an estimate of how far you are from the mains source of the AC field based on the dial settings.

Estimating lower voltages than mains voltage

Assuming the insulation of the wire or cord is similar, set the GT16 to lowest sensitivity and touch the nose to a cord or wire that outputs potential low VAC such as an old style HVAC thermostat. If the thermostat uses 120V or more, it should alarm at close contact similar to when you did calibration. If not, adjust sensitivity up until the alarm starts; the more sensitivity you need, the more likely the output AC is far lower than 120V. Since HVAC thermostats use much smaller wires and insulation, it even reflects more than the voltage is far below mains.

Estimating higher voltages than mains voltage

Assuming the insulation of the wire or cord is similar, set the GT16 to lowest sensitivity and touch the nose to a cord that could output higher VAC such as a 240V dryer. If the GT16 alarms at a distance farther than direct contact with the wire, the field strength is far greater and thus the output AC is above 120V. Often 240V and higher devices also use heavier and thicker insulation, which clues you that the voltage on that line is actually far greater than 120V.

Cons

The alarm should be louder

The LED should be brighter and more an intense RED or Orange. Greenlee should use a translucent yellow or white cover for the sensor as a diffuser for the LED, the transparent plastic has no practical use.

A recessed power button would be better to prevent accidental turn on

The dial should have markings from 1-9, so one can associate the numbers with the calibration

Its more likely to give false positive readings, that is telling users a dangerous voltage exists when there isn't [ note, this could be a Pro, better safe than sorry!]

Pros, beyond the functionality described

Single AAA battery; easy to replace, economical to run, compared to units using 2 AAA or 2 AA or watch battery types. Power consumption: 98mA with LED and beep, 2mA quiet. Battery works down to 1V. On 1.5V AAA Duracell 1000mAH alkaline this is ~ 10 hours of continuous use.

UNDOCUMENTED FEATURE: the GT16 makes a solid continuous beep when on and the battery power is too weak to power the device. Excellent!

Lightweight

High quality plastic polymer, thick, hefty

How durable the unit will last and survive drops remains unknown, however the unit has been in the Greenlee catalog since 2008 and is warranted for life, limited by Greenlee's terms.
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22 of 22 people found the following review helpful
1.0 out of 5 stars DO NOT TRUST THIS TESTER, June 16, 2012
This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
Bought one of these to replace an old Greenlee I had for years. One of the really nice small round yellow ones. I loved the old one so I bought a new Greenlee. Had it for a week, and one day I tested a set of 3 wires for 480v. Checked the wires and read nothing. Checked a 110v outlet and it read voltage. Checked the 480, nothing. Looked at the bus bar and saw the disconnect was turned on. I should read voltage. Try again, and nothing. Put on the wires, and put directly on the screw terminals. Nothing. Tried the 110v, it read voltage. Didn't touch the dial at any time. Tried the 480, nothing. Checked the 480 with a meter, and had 280 on each line! DO NOT TRUST THIS TESTER! I would recommend everyone stay away from this tester.
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7 of 7 people found the following review helpful
1.0 out of 5 stars Beware, January 28, 2012
This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
Have owned and used this tool for about a year. Never really had total trust in the operation because of weird results caused by the sensitivity adjuster. Last week we cut into a 220v cable that showed to be dead regardless of setting. The cable was hot! so now the tool is DEAD - through in the can along with a ruined cutter and pair of drawers. Replaced it with a Klein - hope it is trustworthy.
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6 of 6 people found the following review helpful
5.0 out of 5 stars Greenlee non contact voltage detector for audiophile uses, April 3, 2011
By 
Elizabeth (SE Wisconsin) - See all my reviews
Verified Purchase(What's this?)
This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
I purchased this non contact voltage detector here on Amazon. i am using it to 'sniff' areas of electromagnetic leakage around and in my audiophile stereo system. Cool! Works very well and is much better than comparable products, as it allows easy to verify adjustability and easy use. i had purchased another brand with unmarked buttons which was hard to use and hard to know if it was even ON. So the Greenlee is a bit more expensive than that one, but more than worth the added cost due to it's ease of use.
Excellent tool.
Uses; Find areas of wires which are loose, or not properly shielded. Check if components are adding grunge to the system. A/C wires and interconnect closeness. Instead if struggling to sort them all away from each other, find the ones which are a problem.
this is a great audiophile tool!!!
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6 of 6 people found the following review helpful
4.0 out of 5 stars A Bit Oversensitive?, July 27, 2011
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This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
If you turn the sensitivity all the way up, I swear it sense my body's current. But even all the way down, sometimes it detected current when I knew it was off. Then again, that may be the old house wiring I have. Scary? Anyways, I think it works fine if you know how to use it, but may be it is a tad too sensitive.
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12 of 15 people found the following review helpful
5.0 out of 5 stars Adjustible sensitivity is both good and bad. Makes it less automatic, but more discriminating., June 30, 2011
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This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
I have used a Greenlee detector of this sort that was not adjustable and some other brands, a $3 cheapie and a screwdriver that alerted when you were working on a hot outlet without disconnecting it, after all, I am a gadget geek :-). They worked simply. You touched (or neared, the probes were insulated) the probe to the wires that you were interested in - if the device alerted, the circuit might not be safe. Every time you used it, the instructions warned you to check it on a known hot circuit to insure that it would alert so that you could be sure that if it did not alert the circuits were not hot. While the instructions told you to do it every time you turned it on, most people would probably do it at the beginning of each job phase if they were paranoid (you know, the sort who lives around wires that might be live) and once every couple days if they were not.

But they did not have a high degree of discrimination. Stick the probe into a plug that was attached to a hot socket, and it would alert - on both sides, hot and neutral. It was set to error on the overly sensitive (more alerting) side - so any energy in a wire in the household voltage range kicked it off. One of the devices was worse, it would alert if an adjacent wire in another box was hot even if this circuit was not hot. Sigh, that was a bit too sensitive, but I used that screwdriver to tell me that I had to be extra careful putting this outlet in hot.

Now, this device is actually more interesting. For example, you can adjust the sensitivity to alert when it is "plugged" into the hot side of the plug (again, no actual contact is made, the probe is near the hot conductor insulated by plastic), and not when it is "plugged" into a neutral - pretty simple to adjust it that way. When the sensitivity is all the way up, your one year old can plug it into her belly button and when it flashes and beeps she will giggle because somehow she gets that it is a big game that she has "juice" in her belly button (but not in her ear, because you slide the sensitivity down. Then she learns that with the sensitivity all the way up she can play a simple tune (one note rhythm) by grabbing it differently when the sensitivity is set to max. And it can tell you that the wire from your USB charger is hot.

There is only one control on the device. At one extreme (rolled toward the heel of the device) it clicks to turn the device off. Rolled toward the nose, it clicks to turn the device on. The device starts at max sensitivity. As you continue to roll the control to the nose, the sensitivity decreases. To set it, you have two possibilities, well, three. Possibility one is that you turn it down about an 1/8th turn from "most sensitive" and it will probably be OK, so long as you check it to see if it alerts at all. Possibility two is that one is for looking at clearly hot wires and wire breaks. Stick the probe into the hot side of an outlet and roll the control forward until the alerting stops, then back towards the heel until the alert starts again. It should alert continuously when in the hot side of an outlet and not alert when the probe is stuck in the neutral side of the outlet. Simple, no? Set this way, you should be able to use it to find broken wires, as per the instructions.

As a safety probe, I like it a bit more sensitive. Do the same thing, to start with, but then stick it in the neutral side and continue to roll the control toward the heel until it alerts again. The device should alert when stuck into either side of the outlet, and not alert in the air away from wires. Check it on a live extension cord, it should alert.

This takes a few seconds, and it is not quite as convenient as just turning it on. But if you believe the instructions and if you believe that you can't trust the absence of indication as an indication of safety, you are gonna test your probe when you use it no matter whether it is adjustable or not. To adjust it adds 15 seconds to the setup and allows you to set the sensitivity and alerting the way you want it, and that will save you time on the other end of the job.

I like these devices. IMHO, no one who is working on household circuitry should not have one.

By the way, first time I saw one, the man using it used the probe first and then, if the probe did not react, he checked the circuit again with a multimeter. Why? His logic was that he wanted a fully insulated tool for the first probe in case there was some huge voltage leaking in, and then he wanted to use a different tool that used a different measuring scheme to back that first tool up, because he really did not want to get shocked, burned, or killed.

A few months later he was hospitalized. He wired something in a house up hot, not just an outlet, a subpanel on an existing branch circuit that someone did not want to have disconnected. It took a few seconds lapse and he spent quite a while in the hospital and didn't return to work for a year.

These safety tools only work if you pay attention to them.
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10 of 12 people found the following review helpful
5.0 out of 5 stars good handy product, September 22, 2010
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This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
This is very useful to test high voltage wiring without touching. The adjustable sensitivity feature was why I selected this model. Also AAA battery can last a long time.
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6 of 7 people found the following review helpful
3.0 out of 5 stars eh, December 1, 2010
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This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
not that great. adjustable sensitivity is hit and miss. In my experience it gives false positives and false negatives. In my opinion you're never 100% certain that it's giving you an accurate indication.
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2 of 2 people found the following review helpful
5.0 out of 5 stars A detector to test electriclal service at a camp ground, November 8, 2012
By 
A. D. Baer (Edgewood, NM USA) - See all my reviews
(REAL NAME)   
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This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
Greenlee VT-16 Voltage Detector:
I needed an AC voltage detector (VD) to help make sure that recepticals are wired correctly, before plugging my RV into one of them. The idea was to slide the VD's probe into one of the receptical's slots; the VD is expected to light up if-and-only-if, that slot is hot. Probe all of the receptical's slots. If any are wrong, then the receptical is miss-wired.

I tested four different brands of VD (all sold by Amazon) by using them to probe the slots of correctly wired NEMA 5-15R, L5-30R, TT-30R and L14-30R recepticals. The first three brands failed the by either incorrectly finding a neutral slot to be hot, or a hot slot to be neutral. The Greenlee succeeded in all cases. The Greenlee's 5-1000 VAC adjustable sensitivity made it possible in all environments to pick a sensitivity for which the Greenlee would light up correctly. There are always spots in the environment known to be near 0 VAC. Just pick a sensitivity that is large, but not so large that the Greenlee lights up on those spots.

I gave the Greenlee 5 stars because it did what I needed so well. That is not to say it would do as well in other applications.
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2 of 2 people found the following review helpful
5.0 out of 5 stars A GREAT TOOL, November 27, 2011
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This review is from: Greenlee GT-16 Adjustable Non-Contact Voltage Detector (Tools & Home Improvement)
I had a loose hot wire in my house that was causing 4 lights and six outlets to not function, even though it didn't trip the circuit breaker. Standard troubleshooting practice in this situation is to first check to see if a Ground Fault Interrupt outlet has tripped. Nope, none in this circuit. Next step is to look for problems in the switches, outlets, and light boxes closest to the circuit panel- especially the boundary between working and not working outlets. All electrical fixtures were fine. I hate the next step- go into the attic and look for breaks. That's where this tool comes in really handy. I was able to trace the wires coming up from the circuit panel into the attic by listening to the beep as I ran it along the wires. I got to a junction box under the insulation and the device beeped on the wires going into the box and stopped beeping on the wires that left the box. I turned off the circuit breaker and pulled all of the wires out of the junction box to discover the broken hot wire. It broke because the bend radius on the wire was too small.
You can also use the tool to find the break in the christmas lights.
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Greenlee GT-16 Adjustable Non-Contact Voltage Detector
$23.00 $21.99
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