For what it's worth, In Europe, a ground fault protection device *must*
trigger at no more than 30 milliamps after no more than 30 milliseconds.
There are`also rules about regular testing of fixed installations, & for
testing temporary installations before first use.
** Try reading the whole story.
MK state clearly that ONLY the 30mA models are capable of giving good
The 100 mA models are ONLY intended where a 30 mA one cannot be used -
presumably because inherent circuit leakage to ground equals or exceeds
MK also state the a 300mA model is PURELY intended for equipment and fire
From the point of view of UK wiring regs, RCDs used for protection
against electrocution must be rated at no more than 30mA (and this
is similar in many other countries wiring codes too).
RCDs for protection against high earth fault loop impedance and
not electrocution should be rated at least 100mA. 300mA and 500mA
are common values too.
10mA RCDs as mentioned above are available but are rare. They are
used for protection against electrocution in restrictive conductive
locations (where someone may not be able to remove themselves from
contact with faulty live part due to working in a location which
restricts movement, such as maintenance work inside a pipeline).
10mA RCDs are also suitable for single appliances, but generally
not suitable for circuits feeding many appliances, particularly
Class I IT equipment.
[email address is not usable -- followup in the newsgroup]
** Care to explain you pompous jargon ?
The mysterious phrase " high earth fault loop impedance " don't mean jack
shit to anyone.
The use of plain language is always preferred when addressing an audience.
It's the impedance of the entire circuit if you short the phase cable to
ground, including the LV transformer & feed cable. So divide your phase
voltage by the earth fault impedance & you get the maximum current that
can flow. If that's still gobbldegook then you need some basic knowledge
about electricity to play. Or use google.
Its not "usually" the sound system that creates the hazard
its the guitarist who has a groud fault or has snipped off the ground lug
from his power plug or is incorrectly using a edison adapter wo creates a
when his improperly grounded rig meets the right condition and a properly
grounded rig the current flows from his source(amp) out his guitar cable
into his guitar
now all he has to do is touch his strings and a mic stsand of a properly
grounded system toallow the current to complete its journey to ground
right through his body
"most" sound companies are accutly aware of proper electriacal protocol
most musicians are not
Exactly! I've worked around computers (not here in the USA) where a
ground was not available (a "special" adapter was used to remove the
ground... funny how those adapters are sold in stores), and it *hurts*
when you touch the chassis. 220V, too. We learned very quickly to
shut down the computers before plugging/unplugging devices, to avoid
Even when plugging my laptop into the mains to charge it, I'd get an
unpleasant shock if I even touched the ground around the microphone
Line Out jack.
Oh, here in the USA, the government really CARES about us! haha
In the US, I've seen 2 types of adapters.
One has a 3 pronged outlet with a 2 prong plug and aw ground wire
that is intended to be connected to the screw that holds the plate on.
Assuming that there is a metal box, and it is grounded (big assumptions).
If everything goes as to plan, the 3 pronged outlet should then be fine.
The advantage of the wire is that you can use one in each outlet.
Some people just cut off the wires and ignore the ground (bad plan).
The other style is the same thing except with a spade attached directly
to the plug in such a position that it can be connected directly to the
screw to provide a ground and it locks the adapter onto the outlet
making it more stable. You can only use one on a duplex outlet.
If used correctly, these are fine tools, but using them to lift the ground
is not allowed.
That isn't a situation that you should have to put up with.
Typically a laptop floats and isn't directly connected to ground.
There is probably something connected to it that isn't wired correctly,
or has some other fault. A while back, the RF cable for the cable TV
had quite a bit of kick when referenced to a water pipe ground.
We have fiber running directly to the side of the house now.
It is no longer an issue :-)
They try, but you have to remember that some of "us" are retailers and
manufactures may have a different slant on what caring should be.
Sometimes they have more pull than you or I.
any mains powered electrical equipment operated in the rain
is potentialy lethal unless it is sufficiently protected from water geting
it might not hurt if the microphone got wet,
but if the amp it is connected to got wet ... fizzle hiss zap
do people still use mic cables much for anything larger than a pub
Absolutely. This means putting the stage in a fairly well-protected tent
(which means lousy acoustics, sorry about that), double-insulating the power
system and covering all camlocks and junctions with plastic sheeting. It
means careful grounding, GFIs, and it means a power dispatcher who wanders
around with a meter checking ground fault currents so he has a good idea
when the leakage is getting to the point where a GFI may pop.
It's easy to keep the equipment dry. But keeping the _people_ dry is the
Sure, thousands and thousands of feet of the stuff. It just works, unlike
"C'est un Nagra. C'est suisse, et tres, tres precis."
For example, you can see the umbrellas in the audience and when you
see the shots from behind Bianca - who was the warmup act for Hall &
Oates, you can see it's coming down pretty good. Apparently the
performance was moved to this covered stage because of the weather.
She's using a wireless, even so, could there still be any other
potential hazards to her or others?
It is absolutely essential that all the power circuits have Ground Fault
Circuit Interrupter (GFCI) protection, and that these be tested during
the initial installation. It's also a good idea to surge protect all the
equipment plugged directly into the line. All of the handheld
electricals should have a UL double insulation rating.
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