Re: Field irt resistance
Not sure what you're getting at here. The fields emanate from the conductor and ideally go out to infinity. The resistance has nothing to do with how far the fields propagate from the source. That's a function of the environment they're propagating into.
se
Coolin said:
Not sure what you're getting at here. The fields emanate from the conductor and ideally go out to infinity. The resistance has nothing to do with how far the fields propagate from the source. That's a function of the environment they're propagating into.
se
Coolin""Say we had a wire with a normal resistance compared to an identical wire but now with a much higher resistance.
Will the externaly generated field behave differently?""
The external magnetic field will not behave any differently. And, that is absolutely independent of frequency also, as only the internal field fo the conductor changes when skinning occurs.
The external e field will be changing based on the voltage at every point of the resistor..
Steve: thanks for the information..I figured you would know..
Kinda busy at the moment, but I'll look for some good 3-d drawings showing twisted pair/mag field/loop intercept stuff..cause it's awfully difficult using words..
Sully
Will the externaly generated field behave differently?""
The external magnetic field will not behave any differently. And, that is absolutely independent of frequency also, as only the internal field fo the conductor changes when skinning occurs.
The external e field will be changing based on the voltage at every point of the resistor..
Steve: thanks for the information..I figured you would know..
Kinda busy at the moment, but I'll look for some good 3-d drawings showing twisted pair/mag field/loop intercept stuff..cause it's awfully difficult using words..
Sully
What understanding?
"We seem to have the same understanding here. Which doesn't seem to square with the description Fred quoted from that website which makes some other seemingly bizarre claims."
Some more claims from some other misguided fool.
http://svconline.com/ar/avinstall_cmrr_balanced_interfaces/index.htm
http://www.svconline.com/ar/avinstall_cmrr_balanced_interfaces_2/
I have another question? Why or so many cables designed with twisted pair wires?
I wish I knew how to reduce Emag to simple algebra. It would have made school so much easier.
There are many things that you don't understand. There are many I don't understand. Just because you don't understand something does not make it untrue.
"We seem to have the same understanding here. Which doesn't seem to square with the description Fred quoted from that website which makes some other seemingly bizarre claims."
Some more claims from some other misguided fool.
http://svconline.com/ar/avinstall_cmrr_balanced_interfaces/index.htm
http://www.svconline.com/ar/avinstall_cmrr_balanced_interfaces_2/
I have another question? Why or so many cables designed with twisted pair wires?
I wish I knew how to reduce Emag to simple algebra. It would have made school so much easier.
There are many things that you don't understand. There are many I don't understand. Just because you don't understand something does not make it untrue.
Re: What understanding?
According to a claim made in one of your previous posts, Whitlock is a misguided fool.
In the second article, Whitlock starts out by saying:
A balanced interface can reject any interference — whether because of ground voltage differences, magnetic fields, or electric fields — as long as that interference produces identical voltages, with respect to ground, on each of the signal lines. Because they're common to both inputs, these identical voltages are referred to as the common-mode voltage.
Yet in your previous post, you said:
Noise induced by varying magnetic fields will be differential and not rejected by a balanced circuit, which rejects common mode noise.
If this is true, then Whitlock is incorrect as noise induced by magnetic fields will never be common-mode and therefore there would be no advantage had by using a balanced interface.
So is Whitlock just a shill?
By the way, I note that Whitlock says of twisted pairs:
Twisting of the two wires is a first-order technique to make induced voltages identical by averaging the physical positions of the wires.
Which is what I have been saying and doesn't jibe with the description of how twisting works on the capco.com website.
So is Whitlock incorrect here as well?
Because it's a twisted world out there, Fred.
I never claimed I understood everything. But your hand-waving and offering up what appears to be conflicting information doesn't help anyone understand anything.
se
Fred Dieckmann said:
According to a claim made in one of your previous posts, Whitlock is a misguided fool.
In the second article, Whitlock starts out by saying:
A balanced interface can reject any interference — whether because of ground voltage differences, magnetic fields, or electric fields — as long as that interference produces identical voltages, with respect to ground, on each of the signal lines. Because they're common to both inputs, these identical voltages are referred to as the common-mode voltage.
Yet in your previous post, you said:
Noise induced by varying magnetic fields will be differential and not rejected by a balanced circuit, which rejects common mode noise.
If this is true, then Whitlock is incorrect as noise induced by magnetic fields will never be common-mode and therefore there would be no advantage had by using a balanced interface.
So is Whitlock just a shill?
By the way, I note that Whitlock says of twisted pairs:
Twisting of the two wires is a first-order technique to make induced voltages identical by averaging the physical positions of the wires.
Which is what I have been saying and doesn't jibe with the description of how twisting works on the capco.com website.
So is Whitlock incorrect here as well?
Because it's a twisted world out there, Fred.
I never claimed I understood everything. But your hand-waving and offering up what appears to be conflicting information doesn't help anyone understand anything.
se
Hand waving and hand wringing.
You are so blinded by your ego and personal biases that you seem incapable of learning anything because you won't make the effort. I have given you many respectable references over the last year, and all you seem to do, is manage to read them in the way you want to interpret them, so as not to have learn anything that might go beyond your present level of understanding and present belief system. If the last stuff I sent was not by Bill Whitlock, you would be denying them as well and discrediting them based on your desire to pretend you know better. I am trying help people to understand this stuff and you just don't seem to want to, from what I can see. I wouldn't mind so much if you want to confuse yourself, but you want to confuse people with actual real about things they would like to understand. What are you accomplishing exactly? Personal attacks on me are not going to help anything. I am not interested in telling people what "I" believe, but what engineering text and people with design experience in a given area can explain much better than I can. I even learned some new things in a few of the recent references I found while trying to straighten you out. Contrary to what I think many believe, It not my desire to watch you have a nervous breakdown on the forum. but only to see you stop confusing everybody with your misconceptions. You can rave at me some more, but I really don't what that will accomplish much in the long run. I have a stack of excellent textbooks and love to find good references on the web. I love to learn new things as well as gain further insight into what I know now. It is ironic that in your attempt not to learn anything you are helping to further my education.
Sincerely,
Fred
You are so blinded by your ego and personal biases that you seem incapable of learning anything because you won't make the effort. I have given you many respectable references over the last year, and all you seem to do, is manage to read them in the way you want to interpret them, so as not to have learn anything that might go beyond your present level of understanding and present belief system. If the last stuff I sent was not by Bill Whitlock, you would be denying them as well and discrediting them based on your desire to pretend you know better. I am trying help people to understand this stuff and you just don't seem to want to, from what I can see. I wouldn't mind so much if you want to confuse yourself, but you want to confuse people with actual real about things they would like to understand. What are you accomplishing exactly? Personal attacks on me are not going to help anything. I am not interested in telling people what "I" believe, but what engineering text and people with design experience in a given area can explain much better than I can. I even learned some new things in a few of the recent references I found while trying to straighten you out. Contrary to what I think many believe, It not my desire to watch you have a nervous breakdown on the forum. but only to see you stop confusing everybody with your misconceptions. You can rave at me some more, but I really don't what that will accomplish much in the long run. I have a stack of excellent textbooks and love to find good references on the web. I love to learn new things as well as gain further insight into what I know now. It is ironic that in your attempt not to learn anything you are helping to further my education.
Sincerely,
Fred
Huh....
Been thinkin...
Take a piece of copper wire, and a piece of resistive stuff, both the same dimensions. One naturally has more resistance per length than the other.
Now, measure at HF. Due to skin effect, the copper wire may not be fully utilized, however the resistance wire will have a deeper skin, thus more of it will be used.
I was thinking, obviously it depends on just how much deeper it runs, but would the resistance wire not be more conductive than the Cu at HF?
And BTW, why does it seem to be so very hard to find a good skin effect formula? If there is, why hasn't it been posted here...? I don't see why someone can't come up with a very accurate formula relating dimensions, frequency, resistance and so on?
Tim
Been thinkin...
Take a piece of copper wire, and a piece of resistive stuff, both the same dimensions. One naturally has more resistance per length than the other.
Now, measure at HF. Due to skin effect, the copper wire may not be fully utilized, however the resistance wire will have a deeper skin, thus more of it will be used.
I was thinking, obviously it depends on just how much deeper it runs, but would the resistance wire not be more conductive than the Cu at HF?
And BTW, why does it seem to be so very hard to find a good skin effect formula? If there is, why hasn't it been posted here...? I don't see why someone can't come up with a very accurate formula relating dimensions, frequency, resistance and so on?
Tim
No I think I would like to discuss it right here.
'Which doesn't seem to square with the description Fred quoted from that website which makes some other seemingly bizarre claims."
"By the way, I don't see any physics, engineering, measurements, or anything else of any substance on that web page supporting their local loop claim. Am I supposed to swallow it simply because it's on some company's website?"
"Are all those papers on Jensen's website that Jocko recommended amt go read full of lies?"
"So is Whitlock just a shill?"
"But your hand-waving and offering up what appears to be conflicting information doesn't help anyone understand anything".
In light of such quotes by Mr. Eddy when attempting to reference material to explain some of these topics, I hope that I am not the only one being criticized along this lines. Speculation about personalities seems pretty unnecessary in light of the attitude he shows and statements he makes. His attempts to discredit me now extend to references by very credible sources. It seems that attempts to include anything that doesn't agree with Mr. Eddy's limited understanding of any given topic, results in sarcasm, accusations, and hysteria. This results in essentially censorship to those with views different from his, views based on reason and not an attempt to start a fight every time one responds. I really do want to know what the motivation for these actions are. This is a constantly recurring pattern. This has turned many threads dealing with real questions into rant sessions. I really want to know what the problem is and why we have to put up with this over and over again. I am not the only one who feels this way and don't understand what it is that's positive that the moderators feel Mr. Eddy brings to the forum in threads like this. Is it the entrainment value? I hope not, because it is really at the expense of Mr. Eddy, if that is the case, and he doesn't deserve that.
Sincerely,
Fred Dieckmann
'Which doesn't seem to square with the description Fred quoted from that website which makes some other seemingly bizarre claims."
"By the way, I don't see any physics, engineering, measurements, or anything else of any substance on that web page supporting their local loop claim. Am I supposed to swallow it simply because it's on some company's website?"
"Are all those papers on Jensen's website that Jocko recommended amt go read full of lies?"
"So is Whitlock just a shill?"
"But your hand-waving and offering up what appears to be conflicting information doesn't help anyone understand anything".
In light of such quotes by Mr. Eddy when attempting to reference material to explain some of these topics, I hope that I am not the only one being criticized along this lines. Speculation about personalities seems pretty unnecessary in light of the attitude he shows and statements he makes. His attempts to discredit me now extend to references by very credible sources. It seems that attempts to include anything that doesn't agree with Mr. Eddy's limited understanding of any given topic, results in sarcasm, accusations, and hysteria. This results in essentially censorship to those with views different from his, views based on reason and not an attempt to start a fight every time one responds. I really do want to know what the motivation for these actions are. This is a constantly recurring pattern. This has turned many threads dealing with real questions into rant sessions. I really want to know what the problem is and why we have to put up with this over and over again. I am not the only one who feels this way and don't understand what it is that's positive that the moderators feel Mr. Eddy brings to the forum in threads like this. Is it the entrainment value? I hope not, because it is really at the expense of Mr. Eddy, if that is the case, and he doesn't deserve that.
Sincerely,
Fred Dieckmann
skin depth
delta (skin depth) = square root(2/mu*sigma*omega)
mu = magnetic permeability
sigma = conductivity
omega = frequency
SI units (ugly!)
J.D. Jackson Classical Electrodynamics 3rd Ed page 220 (I used the first...but this one was close)
For Cu at RT he says delta = 6.52(-2)/square root(nu) nu = omega/2*pi = f
since this is SI I believe that delta is in m.
rt
delta (skin depth) = square root(2/mu*sigma*omega)
mu = magnetic permeability
sigma = conductivity
omega = frequency
SI units (ugly!)
J.D. Jackson Classical Electrodynamics 3rd Ed page 220 (I used the first...but this one was close)
For Cu at RT he says delta = 6.52(-2)/square root(nu) nu = omega/2*pi = f
since this is SI I believe that delta is in m.
rt
Re: No I think I would like to discuss it right here.
Look, Fred, you cite references which seem to be at odds with other references you cite. What do you expect me to do? Ignore it?
Just answer me this one question, Fred. If, as you quoted in a previous message, induced noise due to magnetic fields is always differential rather than common-mode, then how can a balanced interface do anything at all about noise induced by magnetic fields? And if it can't, why is Whitlock saying that it can?
How do you expect others to gain anything from information that seems to be in direct contradiction to other information?
se
Fred Dieckmann said:
Look, Fred, you cite references which seem to be at odds with other references you cite. What do you expect me to do? Ignore it?
Just answer me this one question, Fred. If, as you quoted in a previous message, induced noise due to magnetic fields is always differential rather than common-mode, then how can a balanced interface do anything at all about noise induced by magnetic fields? And if it can't, why is Whitlock saying that it can?
How do you expect others to gain anything from information that seems to be in direct contradiction to other information?
se
"...the derivation is for a semi-infinite plane but I suspect that the functional form will apply to wires and the behavior is similar."
The calculation becomes somewhat more complex for a cylinder of finite diameter but the essential relationships remain the same, producing if I remember correctly a slightly increased skin depth for cylinders over planes. For our purposes here it should be accurate enough. I may have the exact equation here somewhere, I'll try to dig it up.
The one advantage of twisted pair geometry that no-one has mentioned here yet is that it significantly reduces the self-inductance of the individual wires due to partial out-of-phase cancellation of the oppositely travelling currents, thus lowering the impedance of the cable at lower frequencies.
The calculation becomes somewhat more complex for a cylinder of finite diameter but the essential relationships remain the same, producing if I remember correctly a slightly increased skin depth for cylinders over planes. For our purposes here it should be accurate enough. I may have the exact equation here somewhere, I'll try to dig it up.
The one advantage of twisted pair geometry that no-one has mentioned here yet is that it significantly reduces the self-inductance of the individual wires due to partial out-of-phase cancellation of the oppositely travelling currents, thus lowering the impedance of the cable at lower frequencies.
cylinder vs plane
if you have the appropriate equation great...and even better if you have a reference to the derivation...I am sure I could do it myself back when I was into it...but I am a bit slower at these things now...so I am sure the derivation is pretty easy to follow and it would be fun to look at.
rt
if you have the appropriate equation great...and even better if you have a reference to the derivation...I am sure I could do it myself back when I was into it...but I am a bit slower at these things now...so I am sure the derivation is pretty easy to follow and it would be fun to look at.
rt
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