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Author Topic: brain storm an optimal human safety system for back line  (Read 96287 times)

Mike Sokol

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Re: brain storm an optimal human safety system for back line
« Reply #140 on: February 05, 2015, 06:30:54 pm »

They have added a touch point similar to neon-based 'screwdriver' tester that will act as a reference point for RPBG testing. By touching that PE-test point it will tell you if your ground is live.

I've not seen that feature on any other socket tester until today...

Is there an English (or American) version of this website? If what you say is true, then that's a real step forward in outlet testing. Do you want beer or donuts???  ;D
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Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #141 on: February 05, 2015, 08:56:00 pm »

Technically, I don't see a safety issue with a bootleg neutral IF you are testing for ground current and  RP.  However, liability wise, if you create a bootleg ground and something fails in your testing you have just put a big target on your back.
 
I commonly hear from electrical inspectors "don't make a non-conforming situation worse, or into another non-conforming situation", but you can leave it as is.

The other possibility is interconnection.  Say your receptacle has no ground so you bootleg-but the guitar amp is connected to a DI that is connected to a mixer that has a ground from another receptacle, now neutral current from your receptacle has another path to ground which may lead to nuisance trips-not necessarily unsafe, but maybe enough to make your device unusable.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #142 on: February 05, 2015, 10:03:13 pm »

Technically, I don't see a safety issue with a bootleg neutral IF you are testing for ground current and  RP.  However, liability wise, if you create a bootleg ground and something fails in your testing you have just put a big target on your back.
 
I commonly hear from electrical inspectors "don't make a non-conforming situation worse, or into another non-conforming situation", but you can leave it as is.

The other possibility is interconnection.  Say your receptacle has no ground so you bootleg-but the guitar amp is connected to a DI that is connected to a mixer that has a ground from another receptacle, now neutral current from your receptacle has another path to ground which may lead to nuisance trips-not necessarily unsafe, but maybe enough to make your device unusable.

Good point... the low liability way is to just not work if anything is not perfect.

JR
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Robert Lofgren

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Re: brain storm an optimal human safety system for back line
« Reply #143 on: February 06, 2015, 03:45:39 am »

Is there an English (or American) version of this website? If what you say is true, then that's a real step forward in outlet testing. Do you want beer or donuts???  ;D
I think I was able to find the actual manufacturer: http://www.dyinstrument.com/duoyi/?q=socket_polarity_tester_RCD/DY207

The common name seems to be dy207 and with a letter at the end to differentiate it from different test configurations.

Here is the product manual. The english version is in the last pages:
http://www.malmbergs.com/docs/ba/4200450.pdf

My only grief about it is that you still need to interpret a led matrix. I'd like it to be more easy and failsafe to read out, with multi color leds to reduce operator error, where red is an error condition and green is OK.

While I like beer (ice-cold kilkenny and/or guinness) I think that I'll have at least one donut with them  :P
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Mike Sokol

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Re: brain storm an optimal human safety system for back line
« Reply #144 on: February 06, 2015, 07:55:06 am »

I think I was able to find the actual manufacturer: http://www.dyinstrument.com/duoyi/?q=socket_polarity_tester_RCD/DY207

The common name seems to be dy207 and with a letter at the end to differentiate it from different test configurations.

Here is the product manual. The english version is in the last pages:
http://www.malmbergs.com/docs/ba/4200450.pdf

My only grief about it is that you still need to interpret a led matrix. I'd like it to be more easy and failsafe to read out, with multi color leds to reduce operator error, where red is an error condition and green is OK.

While I like beer (ice-cold kilkenny and/or guinness) I think that I'll have at least one donut with them  :P

Robert, this is excellent. I've posted a pic of the relevant part of the manual in english. This appears to be a basic 3-light neon tester with an additional neon light connected between the ground contact and an external finger contact. We've discussed the use of a neon bulb for testing hot grounds, so this should work. Of course, this particular tester is for 230 volts only and won't fit an American "Edison" plug, but it should be possible to retrofit an extra neon bulb into a standard 3-light 120-volt Edison outlet tester. The real question is can this tester be UL listed since it could possibly expose the person performing the test to lethal current if the neon bulb and its current limiting resistor both shorted out. Yeah I don't think that double failure mode would be possible, but UL is funny about that sort of thing. What do you all think?
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #145 on: February 06, 2015, 12:28:33 pm »

I appreciate that using a human to complete the NCVT circuit can be made reasonably safe. I believe I can grab a non-contact reference from the output side neutral feed before I power it up. Worst case I might have to plug a unit into the outlet strip for it to detect properly.

=======

Regarding testing for a ground-neutral swap this is less obvious but I am hatching a plan. Perhaps sniff the ground with a small audio amplifier that drives an ear bud or headphone... Clamp it so if you sniff the hot line it doesn't break anything, but I suspect listening to the neutral and ground with almost any product plugged into the same branch circuit should sound characteristically different.  If they sound exactly the same, they are obviously bootleg city.

This will need to grab an environmental ground to work so may require connecting to the human body to provide that audio ground reference. Don't try this at home with anything larger than a .04uF cap in series. Perhaps a little battery powered audio amp?

I need to think about this some more... no easy way to detect hot-neutral swap without taking apart the facility wiring (i.e. interrupt the ground at the panel and see which outlets stop working.  8) ).

JR
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #146 on: February 06, 2015, 05:56:39 pm »

OK, have it buttoned up... wimpy ground wire and not a 300v Y cap but it's good enough for testing the concept.

3 pos switch so one way is hard ground, middle is ground lifted, and other side is 0.047 uF stinger cap.

I just had another interesting thought... If the cap in series with ground limits the current from a 120V fault to 3 mA and the GFCI doesn't trip until 6-7 mA a hot chassis fault will not trip the GFCI.  :o :o :o

Perhaps I need to resize the cap to current limit slightly above the GFCI trip current??

Every data point makes the picture clearer...  Now I will send this to an old friend who is a guitar guy and a design engineer for his first hand opinion. (I don't even have a grounded outlet in my house   :-[  or a guitar amp, or....) I am curious to learn if the .047 cap is quieter than floating the ground.. If I end up with .1uF or more the shielding should be even better.

JR.

PS: Speaking of grounded outlets, I just replaced my extremely tired dishwasher (pump making bad noises) and replaced the former 2 circuit romex power feed with a proper 3 wire line cord. Now both my 3 wire washing machine and 3 wire dishwasher plug into the same 2 wire outlet, in my laundry room. The outlet is literally about 6 feet from my fuse box (still using fuses). I am extremely tempted to drop a GFCI outlet into that box and run my own ground lead the several feet to pickup ground from a screw on the fuse box. Then I would finally have "one" grounded outlet in my house.  ;D
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Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #147 on: February 06, 2015, 07:14:02 pm »

I hope that 2 wire receptacle is GFCI protected-remember, NEC was changed as of 2014 to require GFCI protection for dishwashers.  The story I was told was that the manufacturers could not make the DW safe without GFCI protection.

I have always been OK with fuses-they are more failsafe than breakers, but in the last year I have come across two fuse boxes where the fiber insulating washers in the fuse holders had disintegrated.  Solves the issue of blown fuses, but makes me nervous about them.  Not sure when they quit making home fuse boxes-but they all seem to be getting some age on them these days.

The irony to not having grounded receptacles in your home yet is that in the last few years the actual need for them has diminished greatly-except in the laundry, kitchen and maybe at the computer desk. 
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Steve Swaffer

Robert Lofgren

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Re: brain storm an optimal human safety system for back line
« Reply #148 on: February 06, 2015, 08:49:10 pm »

Robert, this is excellent. I've posted a pic of the relevant part of the manual in english. This appears to be a basic 3-light neon tester with an additional neon light connected between the ground contact and an external finger contact. We've discussed the use of a neon bulb for testing hot grounds, so this should work. Of course, this particular tester is for 230 volts only and won't fit an American "Edison" plug, but it should be possible to retrofit an extra neon bulb into a standard 3-light 120-volt Edison outlet tester. The real question is can this tester be UL listed since it could possibly expose the person performing the test to lethal current if the neon bulb and its current limiting resistor both shorted out. Yeah I don't think that double failure mode would be possible, but UL is funny about that sort of thing. What do you all think?
It is not an actual neon bulb that lights up. I only mentioned that the testing was similar to one. The square above the leds is a lcd that is activated by the PE-test.

It doesn't look like I can open it up without destroying it a little but give me a couple of days before I tear it apart  8)
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Mike Sokol

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Re: brain storm an optimal human safety system for back line
« Reply #149 on: February 07, 2015, 12:49:28 pm »

It is not an actual neon bulb that lights up. I only mentioned that the testing was similar to one. The square above the leds is a lcd that is activated by the PE-test.

It doesn't look like I can open it up without destroying it a little but give me a couple of days before I tear it apart  8)

So you think it's a NCVT built into a 3-light tester? I've been asking for that sort of thing for a long time.
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