Voltage detectors

[TOOL_5150]

Capacitive voltage detectors have certain limitations. Correct operation depends upon the capacitance between the detector’s barrel and ground (normally through your hand and body). If this path is broken for any reason, the detector probably won’t work.

For example, if you’re standing on a wooden ladder, the capacitance between your body and ground will be much less than if you were standing on a concrete floor. To help avoid incorrect detector readings, find an installation ground that you can touch when using the voltage detector. Remember, in a series circuit, the smaller the capacitance, the greater the voltage drop: there might be too much voltage drop from
you to the floor and too little across the detector.

The detectors will also have a certain minimum voltage to turn on. In our wooden ladder scenario, the detector might not turn on despite the circuit being hot. By similar reasoning, the detector cannot detect live conductors inside a grounded metal conduit.

For best results always hold the detector by the body and remember to keep your fingers away from the tip of the detector.




Just made it a littler easier to read.

~Matt

 

[LarryFine]

The following is from a Fluke document.

. . . yada . . . yada . . . yada . . .

As large as I am, I'm confident that I provide a fairly good sized capacitive ground plane reference. :grin: I'm also a little leary of a suggestion to make sure I'm well grounded when testing for a possibly-unknown voltage.

I've never, ever experienced a false negative indication with a good battery. I do the sample-test-sample method. I also double-check by using my K-60 and/or grounding the wire before actually touching them.

Due to how they work, NC testers will respond to induced "phantom" voltages from bundled wires or cables with energized conductors, and they're almost useless in panels, but you don't really need one in a panel.

 

[don_resqcapt19]

Larry,
I have seen the false negative with single conductor USE cables in a muddy ditch and with NM where the paper inside the jacket was wet.

 

[LarryFine]

Larry,
I have seen the false negative with single conductor USE cables in a muddy ditch and with NM where the paper inside the jacket was wet.

Like when the Predator couldn't see Arnold because he was covered with mud.

 

[iwire]

Don, can you point to any OSHA or NIOSH document that says the use of a non contact tester is not acceptable?

Because it seems to me that your position renders these devices worthless.

I will also point out that the power companies seem to use a form of a non contact voltage tester for their work.

 

[ActionDave]

I'm also a little leary of a suggestion to make sure I'm well grounded when testing for a possibly-unknown voltage.

I checked out the instructions for my Amprobe tester and it says to "never ground yourself when taking measurements."

Is there a different technology used in Amprobe vs. Fluke?

 

[don_resqcapt19]

Don, can you point to any OSHA or NIOSH document that says the use of a non contact tester is not acceptable?

I really don't know. My opinion is that the safety rules require the use of a voltage tester and the capacitive devices are voltage detectors or voltage indicators.

Because it seems to me that your position renders these devices worthless.

For the purpose of being sure the power is off to work on a circuit, it is my opinion that the non-contact tester is worthless.

I will also point out that the power companies seem to use a form of a non contact voltage tester for their work.

I don't think the testers that are used for higher voltages work the same way as the capacitive testers that we often have in our pockets.