Hi All,

I have a question relating to plugging my PC into my new 7.1 Amplifier.

To cut to the point, the Coaxial lead coming out of the back of my PC's
sound card digital out(builtin Nvidia Nforce1) gives me a small shock
while holding the end of it (the metal bit) and touching any electronic
equipments metal surface at the same time.

When plugging-in , unplugging into the amp I got a small shock.
Naturally I suppose all electrical leads have power but this seems
unusal.
My question is: Is this normal? I've never known Analog style RCA Red &
White leads to supply enough energy to shock someone (even minimally).
I would want to hold it for more than a second...

This is a new amplifier and although I'd love to continue to use my
computers' 5.1 Coax Out, I'm not too keen if it isn't safe. When i
received this shock, the Set-Top-Box I have connected to the Amp turned
off! , or at least the TV output went black.. i was worried. I simply
reset the STB.

It doesn't seem to be related to the Amp or the Coax Rca style lead i'm
using... Is my computer healthy?

Thanks to anyone who has any idea what is going on here!

Thanks François,
how would I best check whether or not my computer is 'grounded'?
I'm thinking it could be a problem with the cable plugged into the
power supply, the power supply itself, or something else connected to
it that isn't grounded properly. I don't actually have anything else
connected that uses mains power though...
Would you agree that it wouldn't be wise to plug this cable in (its
unusal to get this kind of current isn't it?)


François Yves Le Gal wrote:
On 19 Jun 2006 05:23:11 -0700, "nilo" wrote:

. Is my computer healthy?

This is typically a ground related problem, with some runaway currents
generated by your PC. Check that it's properly grounded, that the digital
out is OK etc.

"nilo" wrote ...

I have a question relating to plugging my PC into
my new 7.1 Amplifier.

To cut to the point, the Coaxial lead coming out
of the back of my PC's sound card digital out(builtin
Nvidia Nforce1) gives me a small shock while holding
the end of it (the metal bit) and touching any electronic
equipments metal surface at the same time.

When plugging-in , unplugging into the amp I got a small
shock. Naturally I suppose all electrical leads have power
but this seems unusal.
My question is: Is this normal? I've never known Analog
style RCA Red & White leads to supply enough energy to
shock someone (even minimally). I would want to hold
it for more than a second...

NO! It is NOT normal. You have a potentially lethal
problem somewhere among your equipment. The
"ground" side of all your equipment (and the attached
cables/connectors) should all be at "ground/earth
potential" (i.e. zero volts).

Suggest immediately abandoning use of this setup
until you diagnose and remedy the problem. Your
life is literally on the line here.

If you don't have a small multi-meter, suggest getting
one NOW. I have seen them even at "home store"
places for $5-10. Start on the 200-300V AC range
and work down from there to measure the voltage
between your two pieces of equipment. If you can
feel it, it is likely at least a couple dozen volts.
"Normal" is zero.

This is a new amplifier and although I'd love to
continue to use my computers' 5.1 Coax Out, I'm not too
keen if it isn't safe. When i received this shock, the
Set-Top-Box I have connected to the Amp turned
off! , or at least the TV output went black.. i was
worried. I simply reset the STB.

It doesn't seem to be related to the Amp or the Coax
Rca style lead i'm using... Is my computer healthy?

Thanks to anyone who has any idea what is going on
here!

Does "set-top box" imply some kind of connection to
television cable system? That is the first place to suspect
a problem. First, disconnect the RF cable from the cable
system and measure the voltage between the outside shell
of the cable connector and the back of the set-top box.
This is a very common place for bad ground problems
because the cable system is referenced to a different ground
than your electrical power mains. There are several sources
of isolation transformers that you can put in-line with the
cable to break this grounding problem.

I can't emphasize enough that this is a potentially lethal
problem. DO NOT continue grabbing the ends of your
cables to feel the shock.

"François Yves Le Gal" wrote ...
"nilo" wrote:
how would I best check whether or not my computer is 'grounded'?

Check your local mains wiring as well as your STB connexions.

I'm thinking it could be a problem with the cable plugged into the
power supply, the power supply itself, or something else connected to
it that isn't grounded properly. I don't actually have anything else
connected that uses mains power though...

The STB can see DC transmitted thru the cable network.

But that is on the inner conductor which is isolated from
the rest of your system.

OTOH, the STB can also see *considerable* AC difference
between the cable system's notion of "ground" and the
ground in your house. Voltages in the mid-50s have been
reported in these newsgroups. At least that is the way
the systems are engineered here in the USA, for better
or for worse. And that is why people sell (and buy)
cable isolation transformers.

I must add, I am using this death trap computer right now, and have
done for a few years now... but I've only just noticed this current
when plugging into its digital audio out...odd

I think I'm gonna have to take a short course in basic electricity and
learn how to use a multimeter, because it doesn't sound like amatuer
stuff

nilo wrote:

Okay Okay Thanks Richard... but I don't think i was quite as clear as I
should have been.,,

Disregarding my Amp, TV, SetTopBox, .. My PC is putting out current
that can give a slight shock on its Coax Digital Audio Out line ... I
just want to know is it normal to feel this kind of current from
touching anything coming out of anything you can easily touch out of
the back of a PC? I tried an altervative RCA cable.. this ( i hope is
what an ordinary to wire analog style audio lead is called)..

A Set-Top-Box is what we call Free-to-air Digital Television recievers
in Australia... we don't have Cable TV only the Satellite Pay TV which
thankgod I haven't got because I watch enough free TV :P

nilo



nilo wrote:

Hi All,

I have a question relating to plugging my PC into my new 7.1 Amplifier.

To cut to the point, the Coaxial lead coming out of the back of my PC's
sound card digital out(builtin Nvidia Nforce1) gives me a small shock
while holding the end of it (the metal bit) and touching any electronic
equipments metal surface at the same time.

When plugging-in , unplugging into the amp I got a small shock.
Naturally I suppose all electrical leads have power but this seems
unusal.
My question is: Is this normal? I've never known Analog style RCA Red &
White leads to supply enough energy to shock someone (even minimally).
I would want to hold it for more than a second...

This is a new amplifier and although I'd love to continue to use my
computers' 5.1 Coax Out, I'm not too keen if it isn't safe. When i
received this shock, the Set-Top-Box I have connected to the Amp turned
off! , or at least the TV output went black.. i was worried. I simply
reset the STB.

It doesn't seem to be related to the Amp or the Coax Rca style lead i'm
using... Is my computer healthy?

Thanks to anyone who has any idea what is going on here!

"nilo" wrote ...
Okay Okay Thanks Richard... but I don't think i was quite as clear as
I
should have been.,,

Disregarding my Amp, TV, SetTopBox, .. My PC is putting out current
that can give a slight shock on its Coax Digital Audio Out line ...

I can't emphasize enough that what feels like
"a slight shock" with dry skin CAN KILL YOU
under the "right" conditions. Fix this now before
it is too late.

On Mon, 19 Jun 2006 07:57:22 -0700, Richard Crowley wrote:


"nilo" wrote ...
Okay Okay Thanks Richard... but I don't think i was quite as clear as
I
should have been.,,

Disregarding my Amp, TV, SetTopBox, .. My PC is putting out current
that can give a slight shock on its Coax Digital Audio Out line ...

I can't emphasize enough that what feels like
"a slight shock" with dry skin CAN KILL YOU
under the "right" conditions. Fix this now before
it is too late.

Yes. I recomend that you don't strip naked and make the connections in the
tub.

In article , "Richard Crowley" wrote:
"François Yves Le Gal" wrote ...
"nilo" wrote:
how would I best check whether or not my computer is 'grounded'?

Check your local mains wiring as well as your STB connexions.

I'm thinking it could be a problem with the cable plugged into the
power supply, the power supply itself, or something else connected to
it that isn't grounded properly. I don't actually have anything else
connected that uses mains power though...

The STB can see DC transmitted thru the cable network.

But that is on the inner conductor which is isolated from
the rest of your system.

OTOH, the STB can also see *considerable* AC difference
between the cable system's notion of "ground" and the
ground in your house. Voltages in the mid-50s have been
reported in these newsgroups. At least that is the way
the systems are engineered here in the USA, for better
or for worse. And that is why people sell (and buy)
cable isolation transformers.

I also understand that the cable should be grounded separately as
it comes into the building. I may be wrong, but it seems like the thing
to do anyway.

greg

nilo wrote:

Hi All,

I have a question relating to plugging my PC into my new 7.1 Amplifier.

To cut to the point, the Coaxial lead coming out of the back of my PC's
sound card digital out(builtin Nvidia Nforce1) gives me a small shock
while holding the end of it (the metal bit) and touching any electronic
equipments metal surface at the same time.

It's an earthing problem.

Graham

Richard Crowley wrote:
If you can feel it, it is likely at least a couple dozen volts.
"Normal" is zero.

Normal isn't zero any more.
Normal is for nothing to be earthed. Any component will have a leakage current
of less than a milliamp, which is legal, but when you connect up an amp, tv,
dvd player etc., then any exposed metal will be floating at 50 or a hundred
volts and can deliver several milliamps.

My guess is that the PC is grounded properly and the shock is from
and touching any electronic equipments metal surface at the same time.

--
Eiron

No good deed ever goes unpunished.

Eiron wrote:

Normal is for nothing to be earthed.

Not for PCs.

Graham

Pooh Bear wrote:


Eiron wrote:

Normal is for nothing to be earthed.

Not for PCs.

Normal is for nothing to be earthed except PCs.

And the solution is to turn everything off at the wall before connecting
the PC's digital coax to the amp.

--
Eiron

No good deed ever goes unpunished.

nilo wrote:
I must add, I am using this death trap computer right now, and have
done for a few years now... but I've only just noticed this current
when plugging into its digital audio out...odd

I think I'm gonna have to take a short course in basic electricity and
learn how to use a multimeter, because it doesn't sound like amatuer
stuff

sf your PC using a 2-wire IEC mains lead rather than the required 3-pins
(wires !).

2-pin ones are available for double-insulated appliances, but are
death-traps when used with appliances that require an earth.

geoff

"GregS" wrote ...

I also understand that the cable should be grounded
separately as it comes into the building. I may be wrong,
but it seems like the thing to do anyway.

The TV cable *is* grounded. It is "code" in most places,
at least here in North America. The problem is not that
it isn't grounded, the problem is that the ground reference
of the cable system is sometimes quite far away from the
ground reference for *your house* (both geographically
"far away" and electrically "far away).

"Richard Crowley" wrote in message
...
I can't emphasize enough that what feels like
"a slight shock" with dry skin CAN KILL YOU
under the "right" conditions. Fix this now before
it is too late.

Maybe you should also emphasise the fact that many devices have enough
leakage to give you quite a tingle, but not enough to kill you.
The days of every chassis/case being tied to a local ground are long gone.

MrT.

"Mr.T" wrote:

"Richard Crowley" wrote in message
...
I can't emphasize enough that what feels like
"a slight shock" with dry skin CAN KILL YOU
under the "right" conditions. Fix this now before
it is too late.

Maybe you should also emphasise the fact that many devices have enough
leakage to give you quite a tingle, but not enough to kill you.
The days of every chassis/case being tied to a local ground are long gone.

There are regulations for Class II ( double insulated ) products. The leakage
current should not be enought to cause a tingle. I've seen tiny sparks when
plugging such things in though ( my printer in fact ) !

Graham

"Mr.T" wrote ...
"Richard Crowley" wrote ...
I can't emphasize enough that what feels like
"a slight shock" with dry skin CAN KILL YOU
under the "right" conditions. Fix this now before
it is too late.

Maybe you should also emphasise the fact that many
devices have enough leakage to give you quite a tingle,
but not enough to kill you.

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

The days of every chassis/
case being tied to a local ground are long gone.

But equipment without protective grounding is required
to have significant "double insulation" instead.

Thankfully, there are people more knowledgable about
these things watching out for your safety.

On Tue, 20 Jun 2006 05:38:39 -0700, "Richard Crowley"
wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

On Tue, 20 Jun 2006 14:03:48 +0100, Laurence Payne
lpayne1NOSPAM@dslDOTpipexDOTcom wrote:

On Tue, 20 Jun 2006 05:38:39 -0700, "Richard Crowley"
wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

The old canard again! The body has a resistance. To get current to
flow through that resistance you need volts (Ohms law applies here as
it does everywhere). If the source resistance of the electricity is
too great to let much current flow, you won't get the volts. Simple
really.

If you have the volts, you will have the amps.

d

--
Pearce Consulting
http://www.pearce.uk.com

On Tue, 20 Jun 2006 14:03:48 +0100, Laurence Payne lpayne1NOSPAM@dslDOTpipexDOTcom wrote:


On Tue, 20 Jun 2006 05:38:39 -0700, "Richard Crowley"
wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

Yes, but current equals volts divided by resistance. For a given
resistance, amperage is proportional to voltage. Static is not
a problem because of it's voltage dies off almost
instantly. Ground yourself well and grab a well charged van de graff
generator and you'll be singing a different story about harmless
static electricity.

On Tue, 20 Jun 2006 13:10:37 GMT, (Don Pearce)
wrote:

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

The old canard again! The body has a resistance. To get current to
flow through that resistance you need volts (Ohms law applies here as
it does everywhere). If the source resistance of the electricity is
too great to let much current flow, you won't get the volts. Simple
really.

If you have the volts, you will have the amps.

Go on then. Measure a few Kv of static and see how many amps you can
draw. The voltage is real and measurable. But there's no amps behind
it. Likewise, use the (very real) voltage between the cable TV
"ground" and your "ground" to do some useful work. That 60v should at
least run a table lamp?

On Tue, 20 Jun 2006 13:46:22 GMT, AZ Nomad
wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

Yes, but current equals volts divided by resistance. For a given
resistance, amperage is proportional to voltage. Static is not
a problem because of it's voltage dies off almost
instantly. Ground yourself well and grab a well charged van de graff
generator and you'll be singing a different story about harmless
static electricity.

Sure. And lightning can kill. But a lot of perfectly real static
voltages we run across in everyday life can't. A rather clumsy straw
man, that :-)

On Tue, 20 Jun 2006 17:47:32 +0100, Laurence Payne
lpayne1NOSPAM@dslDOTpipexDOTcom wrote:

On Tue, 20 Jun 2006 13:10:37 GMT, (Don Pearce)
wrote:

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

The old canard again! The body has a resistance. To get current to
flow through that resistance you need volts (Ohms law applies here as
it does everywhere). If the source resistance of the electricity is
too great to let much current flow, you won't get the volts. Simple
really.

If you have the volts, you will have the amps.

Go on then. Measure a few Kv of static and see how many amps you can
draw. The voltage is real and measurable. But there's no amps behind
it. Likewise, use the (very real) voltage between the cable TV
"ground" and your "ground" to do some useful work. That 60v should at
least run a table lamp?

I've done plenty of static measurements when I had to design a test
system for radiopagers. With typical static sources I was measuring
between 10 and 100 amps. The point is that the pulse is very brief as
there is very little charge behind it all. It is the coulombs, not the
amps that are missing.

As for the PD on a TV, yes it is typically at about half mains
voltage, but that is coupled through a very small capacitance - plenty
enough to run a DMM up to true volts, but not capable of holding up to
deliver current. Even grabbing it by hand, you will typically get a
brief zap, followed by very little.



d

--
Pearce Consulting
http://www.pearce.uk.com

"Laurence Payne" wrote...
"Richard Crowley"wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Amps kill, not volts. Else we'd all be dead many times
over from static discharges.

Oh, here we go again.
Volts kill. It only takes a few mA to stop your heart.
Actually, it is volts * amps = charge.
What do you think they are talking about when the TV
doctor tells the nurse to charge the paddles up to "300"
to revive the patient's stopped heart? Why do you think
they yell "clear!" before applying the charge?

If amps killed, we'd all be dead every time we exchanged
our car battery (good for 300-400 Amperes!)

"Laurence Payne" wrote ...
Sure. And lightning can kill. But a lot of perfectly real static
voltages we run across in everyday life can't. A rather clumsy straw
man, that :-)

And there are just as many (or maybe more) cases where
someone was struck by lightning and they lived to tell
about it. Depends on how much charge when through
them, and whether the current went through any critical
circuits (cardiac, etc.)

On Tue, 20 Jun 2006 17:49:23 +0100, Laurence Payne lpayne1NOSPAM@dslDOTpipexDOTcom wrote:


On Tue, 20 Jun 2006 13:46:22 GMT, AZ Nomad
wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

Yes, but current equals volts divided by resistance. For a given
resistance, amperage is proportional to voltage. Static is not
a problem because of it's voltage dies off almost
instantly. Ground yourself well and grab a well charged van de graff
generator and you'll be singing a different story about harmless
static electricity.

Sure. And lightning can kill. But a lot of perfectly real static
voltages we run across in everyday life can't.

Yes, because a microsecond later, they're under ten volts. Using static
electricity as an example of how high voltage can be OK ignores the fact
that the high voltage vanishs almost immediately.

Richard Crowley wrote:
"Laurence Payne" wrote...
"Richard Crowley"wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Amps kill, not volts. Else we'd all be dead many times
over from static discharges.

Oh, here we go again.

Yes, we all are flying lose and free with terminology and
concepts.

Volts kill. It only takes a few mA to stop your heart.

That's true, but...

Actually, it is volts * amps = charge.

No, volts*amps is NOT charge. volts*amps is power,
measured in watts. Charge is measured in coulombs.

What do you think they are talking about when the TV
doctor tells the nurse to charge the paddles up to "300"
to revive the patient's stopped heart?

They are saying 300 WATT-SECONDS, or 300 joules.
They are talking units of ENERGY, not POWER or CHARGE.

Why do you think
they yell "clear!" before applying the charge?

So everybody can see the patient jump and make googly
eyes?

If amps killed, we'd all be dead every time we exchanged
our car battery (good for 300-400 Amperes!)

Look, so far, NOBODY has got it right or even remotely
complete.

The fact is that electrical conduction through living tissue
is highly non-linear. Under small potential differences,
the electrical conductivity of tissue through the skin is pretty
damned low, and thus the current is similarily low It's not
until enough potential exists that sufficient polarization occurs
that you actually get conduction. Under such circumtances,
the conductivity drops and, if there is sufficient energy left,
then the current starts increasing. Now, IF the current is
sufficient AND the path is right, the current can repolarize
the conduction channels in the cells in muscles and then
there's hell to pay. If the muscles are near the surface of the
skin, then the effect could be anything from a light buzzing
sensation to a sudden contraction. If one of those muscles
happens to be in the ehart, well, a different problem occurs.

All sorts of conditions can change the outcome. Grab on
to a sufficient potential difference when you're hot, dirty,
dripping in sweat and a lot of current could pass, but the
effect could be no more than a sudden urge to drop whatever
it is you're holding NOW! The vast majority of the current flows
in the rather conductive surface moisture on the skin. I myself
have been witness to such a case where the subject accidently
got across of 280 V leg of a three-phase tarnsformer and drew
enough current to blow a breaker, yet walked away with
nothing more than a sore back because the person jumped
and fell. And I have also been witness to someone who almost
killed themselves with about a 20 volt potential between right
knee and left shoulder when the air was cool, dry and most
conduction occured through the skin, but the evidence indicated
that it took several seconds for the conduction to get going.

But to those who say that it's voltage and not amps, you're
wrong. To those that say it's amps that kill and not volts,
you're wrong also.

And to thopse that say the original poster is dealing with a
potentially hazardous situation, well, maybe yes, maybe no.
But precisely what service is being done to this person in
debating on woefully incomplete data and potentially dragging
him down a rosey garden path with tigers hiding in the bushes.

To that poster: find comeone competent to deal with the issue
and FIX IT!

On Tue, 20 Jun 2006 10:12:54 -0700, Richard Crowley wrote:


If amps killed, we'd all be dead every time we exchanged
our car battery (good for 300-400 Amperes!)


Another person clueless of ohms law.

If you touch that battery, you're only pulling a few microamps.

On 6/20/2006 11:49 AM, Laurence Payne wrote:
On Tue, 20 Jun 2006 13:46:22 GMT, AZ Nomad
wrote:

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.
Amps kill, not volts. Else we'd all be dead many times over from
static discharges.
Yes, but current equals volts divided by resistance. For a given
resistance, amperage is proportional to voltage. Static is not
a problem because of it's voltage dies off almost
instantly. Ground yourself well and grab a well charged van de graff
generator and you'll be singing a different story about harmless
static electricity.

Sure. And lightning can kill. But a lot of perfectly real static
voltages we run across in everyday life can't. A rather clumsy straw
man, that :-)

Stand on your right foot and use your right hand. Then the current will
miss your heart.

Don Pearce wrote:

As for the PD on a TV, yes it is typically at about half mains
voltage, but that is coupled through a very small capacitance - plenty
enough to run a DMM up to true volts, but not capable of holding up to
deliver current. Even grabbing it by hand, you will typically get a
brief zap, followed by very little.



--
Eiron

No good deed ever goes unpunished.

"SD" wrote ...
Stand on your right foot and use your right hand. Then the current will
miss your heart.

Is that why left-handed people die younger?

dpierce wrote ...
Richard Crowley wrote:
Actually, it is volts * amps = charge.

No, volts*amps is NOT charge. volts*amps is power,
measured in watts. Charge is measured in coulombs.

Bzzzt! You are right, of course. I shouldn't try thinking
before I wake up.

Why do you think
they yell "clear!" before applying the charge?

So everybody can see the patient jump and make googly
eyes?

LOL! The "googly eyes" part is more Hollywood than
"Real Life".

But to those who say that it's voltage and not amps, you're
wrong. To those that say it's amps that kill and not volts,
you're wrong also.

If I can try to defend myself, my theory was that it takes
enough voltage to make it through the relatively high-
impedance epidermis. OTOH, you could say the same
thing about current from the other side of the Ohm's Law
see-saw.

And to thopse that say the original poster is dealing with a
potentially hazardous situation, well, maybe yes, maybe no.
But precisely what service is being done to this person in
debating on woefully incomplete data and potentially dragging
him down a rosey garden path with tigers hiding in the bushes.

To that poster: find comeone competent to deal with the issue
and FIX IT!

Thanks. That all I was trying to say.

Richard Crowley wrote:

"Mr.T" wrote ...
"Richard Crowley" wrote ...
I can't emphasize enough that what feels like
"a slight shock" with dry skin CAN KILL YOU
under the "right" conditions. Fix this now before
it is too late.

Maybe you should also emphasise the fact that many
devices have enough leakage to give you quite a tingle,
but not enough to kill you.

It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

The days of every chassis/
case being tied to a local ground are long gone.

But equipment without protective grounding is required
to have significant "double insulation" instead.

Thankfully, there are people more knowledgable about
these things watching out for your safety.

Class II ( double insulated ) equipment is still allowed to have a significant (
1mA ) leakage current though.


Graham

Laurence Payne wrote:

On Tue, 20 Jun 2006 13:10:37 GMT, (Don Pearce)
wrote:

Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

The old canard again! The body has a resistance. To get current to
flow through that resistance you need volts (Ohms law applies here as
it does everywhere). If the source resistance of the electricity is
too great to let much current flow, you won't get the volts. Simple
really.

If you have the volts, you will have the amps.

Go on then. Measure a few Kv of static and see how many amps you can
draw. The voltage is real and measurable. But there's no amps behind
it. Likewise, use the (very real) voltage between the cable TV
"ground" and your "ground" to do some useful work. That 60v should at
least run a table lamp?

Oh, there's plenty of amps there, just not many Joules !

Graham

Richard Crowley wrote:

If I can try to defend myself, my theory was that it takes
enough voltage to make it through the relatively high-
impedance epidermis.

You reckon the epidermis works like a zener diode ? Maybe you're right ?

Graham

"Richard Crowley" wrote in message
...
It takes quite a bit of voltage to make it through your
high-impedance epidermis. Several times more voltage
that it would take to kill you under conditions where
your high skin resistance were lowered via any number
of conditions.

Fortunately there is a minimum current required to kill you, and a high
impedance source can not provide it.

The days of every chassis/
case being tied to a local ground are long gone.

But equipment without protective grounding is required
to have significant "double insulation" instead.

Exactly, and if you understood the problem you'd know that's why you can
still get a tingle from metal connectors.
(switch mode power supplies are often the cause)

Thankfully, there are people more knowledgable about
these things watching out for your safety.

Which is why I have had tingles from many double insulated devices I guess.
They are obviously failing to do their job then, in your opinion.

Maybe you think we need regulations to stop us getting a shock from nylon
carpet, or car seat covers as well?
Have many people died from those I wonder.

MrT.

"Don Pearce" wrote in message
...
Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

The old canard again!

You have never had an electrostic shock then?

The body has a resistance. To get current to
flow through that resistance you need volts (Ohms law applies here as
it does everywhere). If the source resistance of the electricity is
too great to let much current flow, you won't get the volts. Simple
really.

Maybe, if you were talking about a permanently connected circuit. It's what
happens at the instant the person touches the voltage that causes the shock.
If the shock continues indefinitelty, there is indeed a fault condition!

If you have the volts, you will have the amps.

If you have enough *source impedance* you will NOT have many amps,
regardless of open circuit voltage.

Simple really.

MrT.

"Don Pearce" wrote in message
...
As for the PD on a TV, yes it is typically at about half mains
voltage, but that is coupled through a very small capacitance - plenty
enough to run a DMM up to true volts, but not capable of holding up to
deliver current. Even grabbing it by hand, you will typically get a
brief zap, followed by very little.

I'm glad you now agree you *can* get a zap from a non faulty device, and not
die.
Seems like your rant was over nothing.

MrT.

On Wed, 21 Jun 2006 13:59:37 +1000, "Mr.T" MrT@home wrote:


"Don Pearce" wrote in message
...
As for the PD on a TV, yes it is typically at about half mains
voltage, but that is coupled through a very small capacitance - plenty
enough to run a DMM up to true volts, but not capable of holding up to
deliver current. Even grabbing it by hand, you will typically get a
brief zap, followed by very little.

I'm glad you now agree you *can* get a zap from a non faulty device, and not
die.
Seems like your rant was over nothing.

MrT.

Rant? I don't remember one of those.

d

--
Pearce Consulting
http://www.pearce.uk.com

On Wed, 21 Jun 2006 13:56:33 +1000, "Mr.T" MrT@home wrote:


"Don Pearce" wrote in message
...
Amps kill, not volts. Else we'd all be dead many times over from
static discharges.

The old canard again!

You have never had an electrostic shock then?

The body has a resistance. To get current to
flow through that resistance you need volts (Ohms law applies here as
it does everywhere). If the source resistance of the electricity is
too great to let much current flow, you won't get the volts. Simple
really.

Maybe, if you were talking about a permanently connected circuit. It's what
happens at the instant the person touches the voltage that causes the shock.
If the shock continues indefinitelty, there is indeed a fault condition!

If you have the volts, you will have the amps.

If you have enough *source impedance* you will NOT have many amps,
regardless of open circuit voltage.

Simple really.

MrT.

If you have the source resistance, you don't get the volts. Simple
really.

d

--
Pearce Consulting
http://www.pearce.uk.com