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Speed and rate of data transfer

by nitin_zilch
Tags: data, rate, speed, transfer
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nitin_zilch
#19
Feb24-13, 10:33 AM
P: 42
Quote Quote by sophiecentaur View Post
How would that work? What would be holding the neutrons together, for a start?
Quote Quote by mfb View Post
There is no solid material with just neutrons. You can use isolators, however, to get a similar effect. Without movable charges, you don't get current flow.
but in case you have a charged battery and you connect it to a bulb through insulators, will the bulb glow? if yes, then why, if no, then why not?
mfb
#20
Feb24-13, 10:40 AM
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No, it will not, there is no (significant) current flow.
sophiecentaur
#21
Feb24-13, 12:10 PM
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This is turning into a nonsense scenario. Electric current is flow of charge. If there are no charges then how can there be a flow?
If you want to get more advanced then Maxwell's Equations involve the consideration of a 'displacement current' for a wave travelling through space but I don't think you are discussing at that level, are you?
davenn
#22
Feb24-13, 01:50 PM
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Quote Quote by sophiecentaur View Post
This is turning into a nonsense scenario. Electric current is flow of charge. If there are no charges then how can there be a flow?
If you want to get more advanced then Maxwell's Equations involve the consideration of a 'displacement current' for a wave travelling through space but I don't think you are discussing at that level, are you?
agreed !!

nitin_zilch you have been given a number of reliable responses in the first page of this thread. Stop going down a path that will destroy the prior quality of the thread

Dave
nitin_zilch
#23
Feb24-13, 09:59 PM
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Quote Quote by davenn View Post
agreed !!

nitin_zilch you have been given a number of reliable responses in the first page of this thread. Stop going down a path that will destroy the prior quality of the thread

Dave
i know i had i a misconception regarding the flow of current, which is highlighted in my question.

i want to know how electromagnetic wave is propogating and is used by the load, consider that the energy available to the load is not in from the kinetic energy of electrons?
Mordred
#24
Feb24-13, 10:44 PM
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As you vary the voltage to the levels that are representing 1's and 0's. Whether that voltage is 5 volt 12 volt etc. Isnt really important.
Higher voltage is higher equates to higher current. Higher current. Signals themselves are varying levels of current. As one signal is sent then another the distance between the two signals stay the same. One does not catch up to the other. Much like sound waves travel through the air. Varying current flows the same way.

The rate of current flow depends on the conductivity of the material your using.
Every gate used in logic requires a certain amount of current to open the gate this is referred to in transistor logic as biasing.
The key is the amount of current per given time.
sophiecentaur
#25
Feb25-13, 03:12 AM
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Quote Quote by nitin_zilch View Post
i know i had i a misconception regarding the flow of current, which is highlighted in my question.

i want to know how electromagnetic wave is propogating and is used by the load, consider that the energy available to the load is not in from the kinetic energy of electrons?
Now that's a real misconception which you need to address. The KE of electrons is an infinitessimal contribution to any energy transferred by 'electricity'. If you have a problem with that then consider a bicycle chain. Is it the KE of the links of the chain that transfers the power from your legs to the wheels? If it were, then the chain would act like a flywheel and the bike would carry on for ages if you removed your feet from the pedals.
The conduction electrons constitute a tiny fraction of the mass of the wires (1/100,000 say) and the drift speed is around 1mm/s. Work out the KE involved.
I think that you are looking for a very convenient and familiar model to describe electromagnetic effects; there isn't one. Read about it - and then read some more, if you want to get this sorted out in your head. Don't just ask more and more wild questions about it. It isn't an efficient way to learn.
carlgrace
#26
Feb26-13, 01:24 PM
P: 555
Back to the original question, it will be quite impossible to send full CMOS-level (5V) signals down 100 meters of any reasonable wire at 1 Gbps. You need a SERDES (serializer-deserializer) to make this happen. Here is a good place to start if you're actually interested in digital communications:

http://www.xilinx.com/publications/a...s/serialio.pdf

I suspect this was just a "theoretical" question. If so, you need to think about the concept of latency. That is, the information can still get from point a to point b but it doesn't have to be instantaneous. Thinking about electrons in a wire is usually not the most useful way to think about a digital communications link. Thinking about EM waves is usually far more fruitful.

As an example of latency, we can send signals to the rover on Mars but there is a 12 minute (or so) latency (depending on orbit). But the information still gets through. How is that possible?
sophiecentaur
#27
Feb26-13, 01:39 PM
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Quote Quote by carlgrace View Post
Back to the original question, it will be quite impossible to send full CMOS-level (5V) signals down 100 meters of any reasonable wire at 1 Gbps. You need a SERDES (serializer-deserializer) to make this happen. Here is a good place to start if you're actually interested in digital communications:

http://www.xilinx.com/publications/a...s/serialio.pdf

I suspect this was just a "theoretical" question. If so, you need to think about the concept of latency. That is, the information can still get from point a to point b but it doesn't have to be instantaneous. Thinking about electrons in a wire is usually not the most useful way to think about a digital communications link. Thinking about EM waves is usually far more fruitful.

As an example of latency, we can send signals to the rover on Mars but there is a 12 minute (or so) latency (depending on orbit). But the information still gets through. How is that possible?
In fact, the black box approach is usually the most successful in engineering. You do the link budget which tells you your likely carrier to noise ratio. This will tell you the likely error statistics for your choice of coding and modulation and you then decide whether it's a pass/fail.

Life is too short to think in terms of studying every link in every chain.
carlgrace
#28
Feb26-13, 01:52 PM
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Quote Quote by sophiecentaur View Post
In fact, the black box approach is usually the most successful in engineering. You do the link budget which tells you your likely carrier to noise ratio. This will tell you the likely error statistics for your choice of coding and modulation and you then decide whether it's a pass/fail.

Life is too short to think in terms of studying every link in every chain.
How true that is. Start with an ideal model and only break open the model as each point fails. Always good advice.

I would say that in a serial link you would be well advised to think more in terms of eye opening rather than C/N. In a serial link it is usually dispersion that kills you, not noise.

Still, if the goal is "understanding" in some sense, then EM waves are a better paradigm than discrete electrons.
sophiecentaur
#29
Feb26-13, 02:59 PM
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Electrons are probably the worst possible introduction to 'electricity'. Never touched them in my early electrical learning. Nowadays they are used by people who have very little understanding of Science to confuse kids with their teaching. And it's not even their fault.
the_emi_guy
#30
Feb26-13, 03:17 PM
P: 589
On the topic of latency of data communications links here are some stats you may find interesting:

At 100 gigabit Ethernet, the spacing between bits on the fiber optic cable is a mere 2mm.
A long reach (40Km) 100GBE link will contain 20 million bits in flight.
Corning Glass has shipped over 30 million Km of long haul (LEAF) fiber.

Thus, at any frozen moment in time, this corresponds to 15 terabits of data in flight within these cables.
sophiecentaur
#31
Feb26-13, 05:48 PM
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Quote Quote by the_emi_guy View Post
On the topic of latency of data communications links here are some stats you may find interesting:

At 100 gigabit Ethernet, the spacing between bits on the fiber optic cable is a mere 2mm.
A long reach (40Km) 100GBE link will contain 20 million bits in flight.
Corning Glass has shipped over 30 million Km of long haul (LEAF) fiber.

Thus, at any frozen moment in time, this corresponds to 15 terabits of data in flight within these cables.
There is a directly similar acoustic situation. When you shout at someone in the distance, your whole sentence may be hanging in the air, on its way to them after you close your mouth finally.
Latency is only a problem when synchronism is important. This can be on a circuit board where line lengths on a Bus need to be equalised to within a mm or two.


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