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I have some old grounded laptop supplies, and didn't see any continuity between the DC side and AC side. Further, in the laptop they'd still also have to have continuity between the DC supply and the USB port.
Most modern Mac laptops have a convertible power supply. You can slide the 3-wire, 8-ft AC power cord off the supply and replace it with a 2-blade plug that's goes directly into the wall outlet. And yes, the 3-wire grounded cord provides a low-impedance path from the outlet safety ground to the chassis of the laptop. I actually demonstrate this in my NoShockZone seminars as a way to reduce ground-loop hum in sound systems.
 

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I use my ideal solenoid tester to check for voltage on a conductive surface.

Place your thumb on the end of one of the test leads and the other lead on the conductive surface. The tester will make noise if voltage is present.
Hmmmm.... That could be dangerous under the right set of circumstances. According to Fluke, those solenoid testers can have an input impedance as low as 1,000 ohms. So lets assume your own hand-to-foot impedance is 1,000 ohms as well, and you're standing on a wet concrete floor. You can now have 60 volts and 60 mA of AC current through your body. At 20 mA you'll lose control of your muscles, which all tense up. This is the point where your hand clamps onto the electrified ladder or wire and you can't let go. And just 30 mA of AC current for a few seconds is considered deadly.

Now, I used to do this same trick using a neon bulb (much safer since it has a 100K input resistance) or a DMM (with a 1+ million ohm resistance) but I still don't think that's worth the risk. That's especially true when you're working alone and want to confirm the wiring is dead before reaching into the outlet.
 

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Why not just get the right tool for the right job?
You'll find that a NCVT (tic-tester) will beep from up to a foot or more away from a large energized surface. Here's a video of me imposing a "hot-skin" potential of up to 120-volts on a 40 ft RV and showing how a Fluke VoltAlert lights up from nearly 2 feet away. Too much fun!!! :thumbup:

http://www.youtube.com/watch?v=Y8h64X33aKg


 

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Mad Skills
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You'll find that a NCVT (tic-tester) will beep from up to a foot or more away from a large energized surface. Here's a video of me imposing a "hot-skin" potential of up to 120-volts on a 40 ft RV and showing how a Fluke VoltAlert lights up from nearly 2 feet away. Too much fun!!! :thumbup:

http://www.youtube.com/watch?v=Y8h64X33aKg


I'm confused...



...at about 5:02 - 5:25 , you state your body is at the same voltage as the RV....but that is not true - your shoes do provide some insulating value, just as they did when you on the cement testing the stairs.
How is your tic-tester NOT showing voltage while you have 120v applied to the RV's skin?

Good tip on the pets, they will probably notice it before a human does :thumbsup:

Give Flash's family my deepest condolences
:laughing:
 

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Anything could be dangerous under the right set of circumstances.

...and the idea is to mitigate those dangers as they apply to you will working.

You realize that using the tester as you described is a recipe for a pine box.
A child, pet or co-worker making contact with you and a grounded surface like a refrigerator or stove might leave a body on the floor.
 

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I'm confused...



...at about 5:02 - 5:25 , you state your body is at the same voltage as the RV....but that is not true - your shoes do provide some insulating value, just as they did when you on the cement testing the stairs.
How is your tic-tester NOT showing voltage while you have 120v applied to the RV's skin?
Actually, compared to the air path between you and ground (which is many hundreds of meg-ohms in standard humidity, and probably a lot more) your damp shoes may be only a few hundred k-ohms (probably less) between you and whatever you're standing on. So yes, if you measured between your human body and the chassis of the energized RV using a very high-impedance voltmeter , you would read zero volts. And testing between an earth ground and yourself or the RV chassis, you would read 120-volts. Seems crazy, but that's how it all works. And since an NCVT (tic-tracer) is capacitively comparing the differential voltage between its tip and the body of the pen where your hand is wrapped around it, then it won't beep while standing inside the energized RV and touching it to a faucet or door frame. But standing inside the RV and pointing it at the ground outside WILL cause it to beep due to the differential voltage. I've confirmed all this with tech support guys from the NCVT manufacturers, so I'm pretty confident that's how it all works.

Give Flash's family my deepest condolences
:laughing:
Don't worry, I've got a lot more flashbulbs.... :thumbup:

Mike Sokol
www.NoShockZone.org
 

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...and the idea is to mitigate those dangers as they apply to you will working.

You realize that using the tester as you described is a recipe for a pine box.
A child, pet or co-worker making contact with you and a grounded surface like a refrigerator or stove might leave a body on the floor.
I appreciate your concern , but let's use that logic in another scenario.
What are my chances of coming in contact with an energized gas or copper water line when crawling under a house?
What are my chances of being in the cross fire of a drive by when working in the hood?

I can come up with many circumstances where I can be killed.

With that way of logic I might as well stay strapped to my sofa.
 

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I can come up with many circumstances where I can be killed.

With that way of logic I might as well stay strapped to my sofa.
But this is also about the safety of your customers, not just yourself.

Since it only takes a few seconds to check an outlet for a hot-ground condition using a NCVT (tic-tester), I believe that all inspectors and electricians should add this quick proximity check to your other testing procedures (Ground Impedance Tester or even a 3-light tester).

I'm not suggesting a tic-tracer (NCVT) as a replacement for testing outlets with a good DMM or INSP-3/SureTest. But adding this additional proximity ground test to your standard outlet test procedure should allow you to find virtually 100% of all outlet mis-wiring conditions.

Your feedback is welcome. I'm an engineer and a bit crazy about measurements, but I want to know what you all think about this from an electrician's point of view.

Mike Sokol
 

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Mad Skills
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I appreciate your concern , but let's use that logic in another scenario.
What are my chances of coming in contact with an energized gas or copper water line when crawling under a house?
What are my chances of being in the cross fire of a drive by when working in the hood?

I can come up with many circumstances where I can be killed.

With that way of logic I might as well stay strapped to my sofa.

You're seriously justifying your callous work practices over a $5 tester?






:blink:
 
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