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Author Topic: What Does ' Grounding ' Equipment do ?  (Read 12018 times)

Offline neilep

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What Does ' Grounding ' Equipment do ?
« on: 27/03/2008 21:20:05 »
Dear Groundologists,

See this ground ?



Now that is quality ground !

Being delivered next Tuesday !

But what does this piece of ground have to do with protecting my electrical components ?



What does ' grounding ' a piece of electrical equipment do to protect it ?


If it gets struck by lightning it's still going to go 'pop ' isn't it ?

What exactly does ' grounding' do ?


I luff ground coffee !

do ewe ?






 

Offline DoctorBeaver

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What Does ' Grounding ' Equipment do ?
« Reply #1 on: 27/03/2008 21:34:57 »
The Earth has charge and has an electromagnetic field. I think that grounding an electric charge passes the current into the Earth where it is absorbed harmlessly by that field.

It works because electricity will always follow the path of least resistance. A grounding circuit gives it an easy path to follow.

From http://hazard.com/library/Electricity/Grounding%20Electricity

Electricity must have an uninterrupted path, or circuit, to follow. If your body becomes part of that circuit, electricity will pass through it. Even with "household" voltage, if your body's resistance to the flow is lowered by wet hands or feet, for example, enough electrical energy can flow through your body to kill you. This is especially true if the electricity passes through vital organs, such as the heart or lungs.

Electricity always follow the path of the least resistance. That's why it is so important to provide an easy path for the current to follow. This is called a ground.

For example, let's say you are holding a drill that has developed a short. Your hands are dry and you are standing on a dry surface. The drill has a ground wire. This means the current will follow the ground wire--not you!

Dry hands and feet offer considerable resistance to household current, but the resistance drops rapidly in the presence of moisture. Portable electric power hand tools are used for many different kinds of work. Unless you are using an acceptable double-insulated electric power tool, you must be absolutely sure that the noncurrent-carrying part are properly grounded.
« Last Edit: 27/03/2008 21:39:08 by DoctorBeaver »
 

lyner

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What Does ' Grounding ' Equipment do ?
« Reply #2 on: 27/03/2008 21:52:27 »
Quote
Electricity always follow the path of the least resistance.
This is a very simplistic statement. The current is 'shared' by all paths. If one path has a lot lower resistance then most of the current takes that path. So, if you connect something to 'Earth' by a low resistance path, that is where most of the current will flow.
If two objects are connected to Earth then, unless there are thousands of amps flowing through the Earth  wires, there cannot be more than a few millivolts of potential difference between them - so no shock or damage.
 

Offline DoctorBeaver

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What Does ' Grounding ' Equipment do ?
« Reply #3 on: 27/03/2008 21:58:07 »
It may be simplistic, but I'm a very simple beaver  :P
 

lyner

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What Does ' Grounding ' Equipment do ?
« Reply #4 on: 27/03/2008 22:28:33 »
Fair enough but sometimes being too simple can lead you into trubble in Science. It only takes 50mA to kill you, if it flows through you for long enough. Your Earth connection has be low enough resistance. . . .
 

Offline DoctorBeaver

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What Does ' Grounding ' Equipment do ?
« Reply #5 on: 28/03/2008 07:39:54 »
That article did go on to say "That's why it is so important to provide an easy path for the current to follow."

I suppose you could argue that it doesn't really tell the whole story.
« Last Edit: 28/03/2008 07:41:50 by DoctorBeaver »
 

Offline that mad man

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What Does ' Grounding ' Equipment do ?
« Reply #6 on: 28/03/2008 20:51:40 »
Grounding can also help in stopping mains hum on sensitive electronic equipment and help with screening against radio frequency interference.

My vinyl record deck has a separate ground point which stops any hum loop from breaking through. Its very important at that stage because of the high amplification required for a record deck cartridge.

You can also get a "floating ground" which may be common to part of the electrical system but not attached to an earth point. Again, I think, designed to eliminate any hum or noise.

 

lyner

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What Does ' Grounding ' Equipment do ?
« Reply #7 on: 28/03/2008 22:30:35 »
Quote
Grounding can also help in stopping mains hum on sensitive electronic equipment

Earths and hum are a constant problem. When people built their own equipment is was a common occurrence to CUT an Earth connection and STOP the hum. It all depends on whether the hum is caused by electric fields or magnetic fields and what the impedance of any high gain elements happens to be.

Professional equipment tends to use 'balanced' signal paths or optical coupling to eliminate hum. It's a minefield.
 

Offline techmind

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What Does ' Grounding ' Equipment do ?
« Reply #8 on: 02/04/2008 14:27:37 »
But what does this piece of ground have to do with protecting my electrical components ?

What does ' grounding ' a piece of electrical equipment do to protect it ?


If it gets struck by lightning it's still going to go 'pop ' isn't it ?
What exactly does ' grounding' do ?

I luff ground coffee !

do ewe ?

I 'luff' ground coffee too!

In wiring and electrical and electronic applications, grounding has many purposes. I wonder if you had any specific case in mind?

As others' have said, one easily comprehended use is the "grounding" of the metal case of appliances and of radiators/pipework etc. This ensures that if a mains/electrical fault arises which shorts the mains to the exposed metal, that current is diverted to ground (and hopefully blows a fuse/trips a circuit breaker) rather than causes the exposed metal to remain at a high voltage and give you a (possibly lethal) shock when you touch it.

In small-signal circuits (including audio), you may have separate "chassis ground" and "signal grounds"! The chassis or "protection" ground is for electrical safety, while the signal ground is the reference against which signals are driven/measured.

All sorts of ground problems ("earth loops", "hum" etc) can arise because owing to the non-zero resistance (and, for high-frequency circuits, inductance) of the ground wiring you can get voltage-drops in it - "ground" may not be equipotential. If you have an electrical loop of ground wiring then if there is an AC magnetic field (eg due to nearby mains wiring) then you can induce circulating currents in the ground wiring ... which typically leads to a lot of frustration!

Safety sidenote, from experience:
CRT TV sets are frequently not earthed, and in practice the outside of the aerial socket and the "ground" on the phono/SCART plugs can aquire 70-80V AC, enough to make a spark and give you a jolt. Also enough to kill other equipment you might connect it to. Be careful plugging and unplugging any electronics which interconnects with a powered TV.
 

Offline neilep

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What Does ' Grounding ' Equipment do ?
« Reply #9 on: 02/04/2008 16:18:39 »
Whoa !!

THANK YOU TMM, SOPHIECENTAUR, DRBEAV & TECHMIND

Je suis well happy avec les answers !

Merci for all your correspondence set forth within this thread.

I always appreciate the time and effort put in by people to respond. The do not got unnoticed and I thank you all. I consider my question sorted !!........

(not Eth...he's just a hairy water rat..Damn him !!....though.....he would say that beavers have feelings too.." To thine own self be true"....)

LOL..wot a load of nonsense !! ;)

Special thanks (enters recipient oscar winning mode) to Techmind who provides a tip for not allowing CRTs shock ewe and more to the point....he also luffs ground coffee !!
 

lyner

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What Does ' Grounding ' Equipment do ?
« Reply #10 on: 05/04/2008 16:41:49 »
Cheers but we are still waiting for our cheques in the post. . . . .
 

Offline techmind

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What Does ' Grounding ' Equipment do ?
« Reply #11 on: 09/04/2008 22:01:58 »
Special thanks (enters recipient oscar winning mode) to Techmind who provides a tip for not allowing CRTs shock ewe and more to the point....he also luffs ground coffee !!

Thankyou. I am greatly honoured...
...er... "glad to be of assistance".
I don't do speeches ;-)

Thanks for the appreciation.
 

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What Does ' Grounding ' Equipment do ?
« Reply #11 on: 09/04/2008 22:01:58 »

 

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