Non contact voltage testing

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DRGREG

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Port Washington, WI, USA, Earth, Etc.
I recently saw a new multi meter that tests both amperage and voltage, on a wire, without contact. When I first saw this new meter I thought that the voltage testing was a real good idea. Then I started to think about what the meter would really be telling me, and the idea popped like a tick. It seems that the meter tests to an arbitrary ground or a lead can be used to connect to a different ground source. In a perfect world everything considered grounded would be bonded to the same source, but the larger problem is "who tests to ground"? Testing to a grounded conductor, or phase to phase, tells me important information, testing across a load or a switching device is uber important, but testing to ground is seldom needed. I guess that you could use this meter as an expensive volt-tic, but I am missing the the practical use for trouble shooting or testing.
 
I have one, it does hertz also. I use it all the time. It shows amps and volts on the same screen, touch a button and it shows hertz. When you want to check phase to phase it has test leads.
 
I understand the absolute necessity of an amp clamp. Knowing the frequency would be useful for troubleshooting motor loads, but it's basically useless for site wiring. The question is, what good is testing voltage to ground? If we take a simple circuit of a t-stat direct controlling an element (I.E. water heater, 240V) and there is no heat, where would you use this non-contact tester to troubleshoot the circuit? Put it around any wire and you have 120V to ground, now you know you have 120V to ground. Is the t-stat open? Is the element open? Is there even 240V to the unit? To test the t-stat, or any similar switch, you test across the switch. To test the element, or any similar load, you test for voltage across the load. Testing to ground tells you nothing. Granted, an ohm meter would be the better tool to use, but i'm questioning voltage testing. I understand that the meter will give you a number, but when my guys tell me a voltage to ground, I ask "who cares"?
 
I don't understand why getting a voltage reading and current reading at the same time is useless. I like seeing what the voltage is while taking a current reading. I do a lot of industrial plant work and knowing if I have a voltage drop problem is a good thing. Now I get that information in one step.
 
I have no idea regarding the accuracy of the voltage readings BUT do a few volts high or low of the nominal make a difference to the average electrician taking readings? If you want accuracy you would use a calibrated meter and possible this meter may meet NIST standards for accuracy.
 
AC current readings are taken a majority of the time with a "non contact" device.

Maybe the one in question here does so without need of encircling the conductor being measured?

Non contact voltage detection about has to be done by measuring capacitive coupling that is involved, this will typically be measuring to ground unless you want to put yourself at same potential as an ungrounded conductor of the same system when testing - but then you get little/no reading if testing to the same system conductor and a reading when testing to grounded objects.

Usefulness can be limited, you must know what you are testing and how/why it works to some extent.

Even the simple volt-tic testers are handy for many things but will mislead people if they don't understand what they are testing. Such testers probably are not acceptable way of verifying absence of voltage for a safety program though. One like you are describing may be better suited then a $5-10 volt-tic tester though.

As you mentioned testing each lead to ground on a water heater thermostat will read ~120 volts to ground, even with physically connected test probes, you need to know that will be normal when switch is open in this case and that you need to check voltage across the switch to test if it is open or closed.
 
The problem is not the accuracy, it's that measuring to ground is a completely useless reading. Voltage is "potential", potential to what? The answer is, potential to another place in the circuit. Ground is a fault path, it's not a part of the circuit. If you have a "grounded conductor" (I.E. a neutral or grounded B phase), this conductor is still not (earth) ground.
 
DRGREG said:
The problem is not the accuracy, it's that measuring to ground is a completely useless reading. Voltage is "potential", potential to what? The answer is, potential to another place in the circuit. Ground is a fault path, it's not a part of the circuit. If you have a "grounded conductor" (I.E. a neutral or grounded B phase), this conductor is still not (earth) ground.
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Usefulness is limited. If all you want to know is if a conductor is energized to other then ground/near ground potential, it might be useful. Determining on/off status of a typical 120 volt circuit is useful - presuming it isn't prone to false readings.
 
kwired said:
Usefulness is limited. If all you want to know is if a conductor is energized to other then ground/near ground potential, it might be useful. Determining on/off status of a typical 120 volt circuit is useful - presuming it isn't prone to false readings.
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Fully half of my testing is satisfied by such methods. The other half does require actual numbers and relation to things other than grounded/ground, though.

I only use high-quality non-contact testers, from Fluke or Klein, and they are diagnostically tested on a known live circuit before each needed test. I'm also used to the idiosyncrasies of those styles. I refuse to use the Greenlee variety as it is far more prone to false positives and has much more trouble distinguishing live conductors in a cable or bundle.

But many safety programs still insist that for absolute assurance, you can't beat a solenoid-type tester like a Wiggy, and there's something to be said for that, assuming you can safely put the probes into contact with the bare conductors for testing.
 
I started this post because I believe that those in our trade need to use only the best possible practices when testing or troubleshooting circuits. I hope this makes just one person find a deeper understanding of the complexity of what so many think is "simple". I want to tell everyone here that what we do is far from simple, and that is why WE do it. I do see some legitimate uses for this type of tester, my concern is that it will simplify bad testing methods. So next time you are testing to ground, with or without leads, take time to think about the measurement you get, and how it relates to the circuit.
Merry Christmas to all, I hope you find a Fluke under your tree...,
DRGREG
 
First I will say I hardly ever use them and even somewhat despise them. I do think they are an important safety item however.

I work at a hospital so my electrical systems are relatively safe and maintained. If I was working in the field where a service entrance neutral was open at the pole, and ground rods were compromised, I might be really glad I had such a meter before I put my hands on the panel.

In short they have their place and limitations. I certainly wouldn’t label them as useless. Nor would I call a voltage measurement to ground useless. I do hear what you are saying but think it misses some things.
 
Russs57 said:
First I will say I hardly ever use them and even somewhat despise them. I do think they are an important safety item however.

I work at a hospital so my electrical systems are relatively safe and maintained. If I was working in the field where a service entrance neutral was open at the pole, and ground rods were compromised, I might be really glad I had such a meter before I put my hands on the panel.

In short they have their place and limitations. I certainly wouldn’t label them as useless. Nor would I call a voltage measurement to ground useless. I do hear what you are saying but think it misses some things.
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I agree with you when talking about the average pen type non contact voltage tester. I believe OP is talking about something of much higher quality that probably is much less likely to false readings, sounds even like it may actually give a voltage reading or at least a reading within a certain range and not just energized/de-energized type readings.
 
kwired said:
...I believe OP is talking about something of much higher quality that probably is much less likely to false readings, sounds even like it may actually give a voltage reading or at least a reading within a certain range and not just energized/de-energized type readings.
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Agreed. Too bad he didn't remember a make or model, and I've not gotten around to trying to find what he's thinking about yet.
 
Correct, http://en-us.fluke.com/products/electrical-testers/t6-1000-electrical-tester.html
I did not put the make and model in the thread because I didn't think that it was that important. So sorry. The issue is that there are few instances where measuring from a wire to ground (earth) is needed. This product will not tell you if your tub is hot, unless you use the leads. I would not use a non contact type meter to troubleshoot combined neutrals, back EMF, harmonics problems, or any grounding issue. This thread does indicate how some people are testing voltage incorrectly and thinking they have the answer. As stated earlier, I think that this type of meter will make it even easier to get crappy data, which is really bad for someone whose understanding of the circuit is already questionable. In conclusion I'm not one to blame the tool, but this feature is screaming for some blame.
 
DRGREG said:
...It seems that the meter tests to an arbitrary ground or a lead can be used to connect to a different ground source. In a perfect world everything considered grounded would be bonded to the same source, but the larger problem is "who tests to ground"? Testing to a grounded conductor, or phase to phase, tells me important information, testing across a load or a switching device is uber important, but testing to ground is seldom needed. I guess that you could use this meter as an expensive volt-tic, but I am missing the the practical use for trouble shooting or testing.
Click to expand...

I wouldn't say "ground" is arbitrary. As far as the meter goes, Fluke says: "Requires capacitive path to ground, provided through user in most applications.
Ground connection via test lead may be required in some situations."

As mentioned, At least half of my testing is satisfied with testing to ground. I'm considering getting one and putting it through some paces. I'm comparison shopping right now between the T5 and T6 models, each available in 600 and 1000 V versions.

https://www.fluke-direct.com/pdfs/cache/www.fluke-direct.com/t6-1000/datasheet/t6-1000-datasheet.pdf
 
At the Seattle NECA show, the rep at the Fluke booth explained this new meter works the same as a Tic Tracer, it depends on your body capacitance to ground to work. If you are on a ladder there is a separate ground lead to connect up.
Its a clever and useful meter but its important to understand how it works and limitations.
I would not use it to very the absence of voltage for LOTO, but its good to measure for troubleshooting
 
tom baker said:
At the Seattle NECA show, the rep at the Fluke booth explained this new meter works the same as a Tic Tracer, it depends on your body capacitance to ground to work. If you are on a ladder there is a separate ground lead to connect up. ...
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In that case, wouldn't the construction of your shoes make a difference? Do you have to know ahead of time if you will have a sufficient capacitive path, and ground it accordingly if not, or will the meter tell you that you don't? Will it give false readings without telling you your capacitive path is insufficient? I'm going to look for some detailed reviews from actual users before I buy one.
 
MAC702 said:
In that case, wouldn't the construction of your shoes make a difference? Do you have to know ahead of time if you will have a sufficient capacitive path, and ground it accordingly if not, or will the meter tell you that you don't? Will it give false readings without telling you your capacitive path is insufficient? I'm going to look for some detailed reviews from actual users before I buy one.
Click to expand...
I was thinking along same line, even standing on wood vs concrete or things like that will make a difference

Was also wondering what happens if you connected "ground lead" to an ungrounded conductor?
 
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